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Past stories here have explored the myriad criminal uses of a hacked computer, the various ways that your inbox can be spliced and diced to help cybercrooks ply their trade, and the value of a hacked company. Today’s post looks at the price of stolen credentials for just about any e-commerce, bank site or popular online service, and provides a glimpse into the fortunes that an enterprising credential thief can earn selling these accounts on consignment.

Not long ago in Internet time, your typical cybercriminal looking for access to a specific password-protected Web site would most likely visit an underground forum and ping one of several miscreants who routinely leased access to their “bot logs.”

These bot log sellers were essentially criminals who ran large botnets (collections of hacked PCs) powered by malware that can snarf any passwords stored in the victim’s Web browser or credentials submitted into a Web-based login form. For a few dollars in virtual currency, a ne’er-do-well could buy access to these logs, or else he and the botmaster would agree in advance upon a price for any specific account credentials sought by the buyer.

Back then, most of the stolen credentials that a botmaster might have in his possession typically went unused or unsold (aside from the occasional bank login that led to a juicy high-value account). Indeed, these plentiful commodities held by the botmaster for the most part were simply not a super profitable line of business and so went largely wasted, like bits of digital detritus left on the cutting room floor.

But oh, how times have changed! With dozens of sites in the underground now competing to purchase and resell credentials for a variety of online locations, it has never been easier for a botmaster to earn a handsome living based solely on the sale of stolen usernames and passwords alone.

If the old adage about a picture being worth a thousand words is true, the one directly below is priceless because it illustrates just how profitable the credential resale business has become.

The image shown above is the wholesaler division of “Carder’s Paradise,” a bustling dark web service that sells credentials for hundreds of popular Web destinations. The screen shot above is an earnings panel akin to what you would see if you were a seller of stolen credentials to this service — hence the designation “Seller’s Paradise” in the upper left hand corner of the screen shot.

This screen shot was taken from the logged-in account belonging to one of the more successful vendors at Carder’s Paradise. We can see that in just the first seven months of 2017, this botmaster sold approximately 35,000 credential pairs via the Carder’s Paradise market, earning him more than $288,000. That’s an average of $8.19 cents for each credential sold through the service.

Bear in mind that this botmaster only makes money based on consignment: Regardless of how much he uploads to Seller’s Paradise, he doesn’t get paid for any of it unless a Seller’s Paradise customer chooses to buy what he’s selling.

Fortunately for this guy, almost 9,000 different customers of Seller’s Paradise chose to purchase one or more of his username and password pairs. It was not possible to tell from this seller’s account how many credential pairs total that he has contributed to this service which went unsold, but it’s a safe bet that it was far more than 35,000.

[A side note is in order here because there is some delicious irony in the backstory behind the screenshot above: The only reason a source of mine was able to share it with me was because this particular seller re-used the same email address and password across multiple unrelated cybercrime services].

Based on the prices advertised at Carder’s Paradise (again, Carder’s Paradise is the retail/customer side of Seller’s Paradise) we can see that the service on average pays its suppliers about half what it charges customers for each credential. The average price of a credential for more than 200 different e-commerce and banking sites sold through this service is approximately $15.

Indeed, fifteen bucks is exactly what it costs to buy stolen logins for airbnb.com, comcast.com, creditkarma.com, logmein.com and uber.com. A credential pair from AT&T Wireless — combined with access to the victim’s email inbox — sells for $30.

The most expensive credentials for sale via this service are those for the electronics store frys.com ($190). I’m not sure why these credentials are so much more expensive than the rest, but it may be because thieves have figured out a reliable and very profitable way to convert stolen frys.com customer credentials into cash.

Usernames and passwords to active accounts at military personnel-only credit union NavyFederal.com fetch $60 apiece, while credentials to various legal and data aggregation services from Thomson Reuters properties command a $50 price tag.

The full price list of credentials for sale by this dark web service is available in this PDF. For CSV format, see this link. Both lists are sorted alphabetically by Web site name.

This service doesn’t just sell credentials: It also peddles entire identities — indexed and priced according to the unwitting victim’s FICO score. An identity with a perfect credit score (850) can demand as much as $150.

And of course this service also offers the ability to pull full credit reports on virtually any American — from all three major credit bureaus — for just $35 per bureau.

Plenty of people began freaking out earlier this year after a breach at big-three credit bureau Equifax jeopardized the Social Security Numbers, dates of birth and other sensitive date on more than 145 million Americans. But as I have been trying to tell readers for many years, this data is broadly available for sale in the cybercrime underground on a significant portion of the American populace.

If the threat of identity theft has you spooked, place a freeze on your credit file and on the file of your spouse (you may even be able to do this for your kids). Credit monitoring is useful for letting you know when someone has stolen your identity, but these services can’t be counted on to stop an ID thief from opening new lines of credit in your name.

They are, however, useful for helping to clean up identity theft after-the-fact. This story is already too long to go into the pros and cons of credit monitoring vs. freezes, so I’ll instead point to a recent primer on the topic and urge readers to check it out.

Finally, it’s a super bad idea to re-use passwords across multiple sites. KrebsOnSecurity this year has written about multiple, competing services that sell or sold access to billions of usernames and passwords exposed in high profile data breaches at places like Linkedin, Dropbox and Myspace. Crooks pay for access to these stolen credential services because they know that a decent percentage of Internet users recycle the same password at multiple sites.

One alternative to creating and remembering strong, lengthy and complex passwords for every important site you deal with is to outsource this headache to a password manager.  If the online account in question allows 2-factor authentication (2FA), be sure to take advantage of that.

Two-factor authentication makes it much harder for password thieves (or their customers) to hack into your account just by stealing or buying your password: If you have 2FA enabled, they also would need to hack that second factor (usually your mobile device) before being able to access your account. For a list of sites that support 2FA, check out twofactorauth.org.

On Dec. 6, 2017, approximately USD $52 million worth of Bitcoin mysteriously disappeared from the coffers of NiceHash, a Slovenian company that lets users sell their computing power to help others mine virtual currencies. As the investigation into the heist nears the end of its second week, many Nice-Hash users have expressed surprise to learn that the company’s chief technology officer recently served several years in prison for operating and reselling a massive botnet, and for creating and running ‘Darkode,” until recently the world’s most bustling English-language cybercrime forum.

In December 2013, NiceHash CTO Matjaž Škorjanc was sentenced to four years, ten months in prison for creating the malware that powered the ‘Mariposa‘ botnet. Spanish for “Butterfly,” Mariposa was a potent crime machine first spotted in 2008. Very soon after, Mariposa was estimated to have infected more than 1 million hacked computers — making it one of the largest botnets ever created.

ButterFly Bot, as it was more commonly known to users, was a plug-and-play malware strain that allowed even the most novice of would-be cybercriminals to set up a global operation capable of harvesting data from thousands of infected PCs, and using the enslaved systems for crippling attacks on Web sites. The ButterFly Bot kit sold for prices ranging from $500 to $2,000.

Prior to his initial arrest in Slovenia on cybercrime charges in 2010, Škorjanc was best known to his associates as “Iserdo,” the administrator and founder of the exclusive cybercrime forum Darkode.

On Darkode, Iserdo sold his Butterfly Bot to dozens of other members, who used it for a variety of illicit purposes, from stealing passwords and credit card numbers from infected machines to blasting spam emails and hijacking victim search results. Microsoft Windows PCs infected with the bot would then try to spread the disease over MSN Instant Messenger and peer-to-peer file sharing networks.

In July 2015, authorities in the United States and elsewhere conducted a global takedown of the Darkode crime forum, arresting several of its top members in the process. The U.S. Justice Department at the time said that out of 800 or so crime forums worldwide, Darkode represented “one of the gravest threats to the integrity of data on computers in the United States and around the world and was the most sophisticated English-speaking forum for criminal computer hackers in the world.”

Following Škorjanc’s arrest, Slovenian media reported that his mother Zdenka Škorjanc was accused of money laundering; prosecutors found that several thousand euros were sent to her bank account by her son. That case was dismissed in May of this year after prosecutors conceded she probably didn’t know how her son had obtained the money.

Matjaž Škorjanc did not respond to requests for comment. But local media reports state that he has vehemently denied any involvement in the disappearance of the NiceHash stash of Bitcoins.

In an interview with Slovenian news outlet Delo.si, the NiceHash CTO described the theft “as if his kid was kidnapped and his extremities would be cut off in front of his eyes.” A roughly-translated English version of that interview has been posted to Reddit.

According to media reports, the intruders were able to execute their heist after stealing the credentials of a user with administrator privileges at NiceHash. Less than an hour after breaking into the NiceHash servers, approximately 4,465 Bitcoins were transferred out of the company’s accounts.

A source close to the investigation told KrebsOnSecurity that the NiceHash hackers used a virtual private network (VPN) connection with a Korean Internet address, although the source said Slovenian investigators were reluctant to say whether that meant South Korea or North Korea because they did not want to spook the perpetrators into further covering their tracks.

CNN, Bloomberg and a number of other Western media outlets reported this week that North Korean hackers have recently doubled down on efforts to steal, phish and extort Bitcoins as the price of the currency has surged in recent weeks.

“North Korean hackers targeted four different exchanges that trade bitcoin and other digital currencies in South Korea in July and August, sending malicious emails to employees, according to police,” CNN reported.

Bitcoin’s blockchain ledger system makes it easy to see when funds are moved, and NiceHash customers who lost money in the theft have been keeping a close eye on the Bitcoin payment address that received the stolen funds ever since. On Dec. 13, someone in control of that account began transferring the stolen bitcoins to other accounts, according to this transaction record.

The NiceHash theft occurred as the price of Bitcoin was skyrocketing to new highs. On January 1, 2017, a single Bitcoin was worth approximately $976. On December 6, the day of the NiceHash hack, had ballooned to $11,831.

Today, a single Bitcoin can be sold for more than $17,700, meaning whoever is responsible for the NiceHash hack has seen their loot increase in value by roughly $27 million since the theft.

In a post on its homepage, NiceHash said it was in the final stages of re-launching the surrogate mining service.

“Your bitcoins were stolen and we are working with international law enforcement agencies to identify the attackers and recover the stolen funds. We understand it may take some time and we are working on a solution for all users that were affected.

“If you have any information about the attack, please email us at [email protected]. We are giving BTC rewards for the best information received. You can also join our community page about the attack on reddit.“

However, many followers of NiceHash’s Twitter account said they would not be returning to the service unless and until their stolen Bitcoins were returned.

The U.S. Justice Department on Tuesday unsealed the guilty pleas of two men first identified in January 2017 by KrebsOnSecurity as the likely co-authors of Mirai, a malware strain that remotely enslaves so-called “Internet of Things” devices such as security cameras, routers, and digital video recorders for use in large scale attacks designed to knock Web sites and entire networks offline (including multiple major attacks against this site).

Entering guilty pleas for their roles in developing and using Mirai are 21-year-old Paras Jha from Fanwood, N.J. and Josiah White, 20, from Washington, Pennsylvania.

Jha and White were co-founders of Protraf Solutions LLC, a company that specialized in mitigating large-scale DDoS attacks. Like firemen getting paid to put out the fires they started, Jha and White would target organizations with DDoS attacks and then either extort them for money to call off the attacks, or try to sell those companies services they claimed could uniquely help fend off the attacks.

CLICK FRAUD BOTNET

In addition, the Mirai co-creators pleaded guilty to charges of using their botnet to conduct click fraud — a form of online advertising fraud that will cost Internet advertisers more than $16 billion this year, according to estimates from ad verification company Adloox. 

The plea agreements state that Jha, White and another person who also pleaded guilty to click fraud conspiracy charges — a New Orleans man named Dalton Norman — leased access to their botnet for the purposes of earning fraudulent advertising revenue through click fraud activity and renting out their botnet to other cybercriminals.

As part of this scheme, victim devices were used to transmit high volumes of requests to view web addresses associated with affiliate advertising content. Because the victim activity resembled legitimate views of these websites, the activity generated fraudulent profits through the sites hosting the advertising content, at the expense of online advertising companies.

Jha and his co-conspirators admitted receiving as part of the click fraud scheme approximately two hundred bitcoin, valued on January 29, 2017 at over $180,000.

Prosecutors say Norman personally earned over 30 bitcoin, valued on January 29, 2017 at approximately $27,000. The documents show that Norman helped Jha and White discover new, previously unknown vulnerabilities in IoT devices that could be used to beef up their Mirai botnet, which at its height grew to more than 300,000 hacked devices.

MASSIVE ATTACKS

The Mirai malware is responsible for coordinating some of the largest and most disruptive online attacks the Internet has ever witnessed. The biggest and first to gain widespread media attention began on Sept. 20, 2016, when KrebsOnSecurity came under a sustained distributed denial-of-service attack from more than 175,000 IoT devices (the size estimates come from this Usenix paper (PDF) on the Mirai botnet evolution).

That September 2016 digital siege maxed out at 620 Gbps, almost twice the size of the next-largest attack that Akamai — my DDoS mitigation provider at the time — had ever seen.

The attack continued for several days, prompting Akamai to force my site off of their network (they were providing the service pro bono, and the attack was starting to cause real problems for their paying customers). For several frustrating days this Web site went dark, until it was brought under the auspices of Google’s Project Shield, a program that protects journalists, dissidents and others who might face withering DDoS attacks and other forms of digital censorship because of their publications.

At the end of September 2016, just days after the attack on this site, the authors of Mirai — who collectively used the nickname “Anna Senpai” — released the source code for their botnet. Within days of its release there were multiple Mirai botnets all competing for the same pool of vulnerable IoT devices.

Some of those Mirai botnets grew quite large and were used to launch hugely damaging attacks, including the Oct. 21, 2016 assault against Internet infrastructure firm Dyn that disrupted Twitter, Netflix, Reddit and a host of other sites for much of that day.

The leak of the Mirai source code led to the creation of dozens of copycat Mirai botnets, all of which were competing to commandeer the same finite number of vulnerable IoT devices. One particularly disruptive Mirai variant was used in extortion attacks against a number of banks and Internet service providers in the United Kingdom and Germany.

In July 2017, KrebsOnSecurity published a story following digital clues that pointed to a U.K. man named Daniel Kaye as the apparent perpetrator of those Mirai attacks. Kaye, who went by the hacker nickname “Bestbuy,” was found guilty in Germany of launching failed Mirai attacks that nevertheless knocked out Internet service for almost a million Deutsche Telekom customers, for which he was given a suspended sentence. Kaye is now on trial in the U.K. for allegedly extorting banks in exchange for calling off targeted DDoS attacks against them.

Not long after the Mirai source code was leaked, I began scouring cybercrime forums and interviewing people to see if there were any clues that might point to the real-life identities of Mirai’s creators.

On Jan 18, 2017, KrebsOnSecurity published the results of that four-month inquiry, Who is Anna Senpai, the Mirai Worm Author? The story is easily the longest in this site’s history, and it cited a bounty of clues pointing back to Jha and White — two of the men whose guilty pleas were announced today.

According to my reporting, Jha and White primarily used their botnet to target online gaming servers — particularly those tied to the hugely popular game Minecraft. Around the same time as the attack on my site, French hosting provider OVH was hit with a much larger attack from the same Mirai botnet (see image above), and the CTO of OVH confirmed that the target of that attack was a Minecraft server hosted on his company’s network.

My January 2017 investigation also cited evidence and quotes from associates of Jha who said they suspected he was responsible for a series of DDoS attacks against Rutgers University: During the same year that Jha began studying at the university for a bachelor’s degree in computer science, the school’s servers came under repeated, massive attacks from Mirai.

With each DDoS against Rutgers, the attacker — using the nicknames “og_richard_stallman,” “exfocus” and “ogexfocus,” — would taunt the university in online posts and media interviews, encouraging the school to spend the money to purchase some kind of DDoS mitigation service.

It remains unclear if Jha (and possibly others) may face separate charges in New Jersey related to his apparent Mirai attacks on Rutgers. According to a sparsely-detailed press release issued Tuesday afternoon, the Justice Department is slated to hold a media conference at 2 p.m. today with officials from Alaska (where these cases originate) to “discuss significant cybercrime cases.”

Update: 11:43 a.m. ET: The New Jersey Ledger just published a story confirming that Jha also has pleaded guilty to the Rutgers DDoS attacks, as part of a separate case lodged by prosecutors in New Jersey.

PAYBACK

Under the terms of his guilty plea in the click fraud conspiracy, Jha agreed to give up 13 bitcoin, which at current market value of bitcoin (~$17,000 apiece) is nearly USD $225,000.

Jha will also waive all rights to appeal the conviction and whatever sentence gets imposed as a result of the plea. For the click fraud conspiracy charges, Jha, White and Norman each face up to five years in prison and a $250,000 fine.

In connection with their roles in creating and ultimately unleashing the Mirai botnet code, Jha and White each pleaded guilty to one count of conspiracy to violate 18 U.S.C. 1030(a)(5)(A). That is, to “causing intentional damage to a protected computer, to knowingly causing the transmission of a program, code, or command to a computer with the intention of impairing without authorization the integrity or availability of data, a program, system, or information.”

For the conspiracy charges related to their authorship and use of Mirai, Jha and White likewise face up to five years in prison, a $250,000 fine, and three years of supervised release.

This is a developing story. Check back later in the day for updates from the DOJ press conference, and later in the week for a follow-up piece on some of the lesser-known details of these investigations.

The Justice Department unsealed the documents related to these cases late in the day on Tuesday. Here they are:

Jha click fraud complaint (PDF)
Jha click fraud plea (PDF)
Jha DDoS/Mirai complaint (PDF)
Jha DDoS/Mirai plea (PDF)
White DDoS complaint (PDF)
White DDoS/Mirai Plea (PDF)
Norman click fraud complaint (PDF)
Norman click fraud plea (PDF)

The final Patch Tuesday of the year is upon us, with Adobe and Microsoft each issuing security updates for their software once again. Redmond fixed problems with various flavors of Windows, Microsoft Edge, Office, Exchange and its Malware Protection Engine. And of course Adobe’s got another security update available for its Flash Player software.

The December patch batch addresses more than 30 vulnerabilities in Windows and related software. As per usual, a huge chunk of the updates from Microsoft tackle security problems with the Web browsers built into Windows.

Also in the batch today is an out-of-band update that Microsoft first issued last week to fix a critical issue in its Malware Protection Engine, the component that drives the Windows Defender/Microsoft Security Essentials embedded in most modern versions of Windows, as well as Microsoft Endpoint Protection, and the Windows Intune Endpoint Protection anti-malware system.

Microsoft was reportedly made aware of the malware protection engine bug by the U.K.’s National Cyber Security Centre (NCSC), a division of the Government Communications Headquarters — the United Kingdom’s main intelligence and security agency. As spooky as that sounds, Microsoft said it is not aware of active attacks exploiting this flaw.

Microsoft said the flaw could be exploited via a booby-trapped file that gets scanned by the Windows anti-malware engine, such as an email or document. The issue is fixed in version 1.1.14405.2 of the engine. According to Microsoft, Windows users should already have the latest version because the anti-malware engine updates itself constantly. In any case, for detailed instructions on how to check whether your system has this update installed, see this link.

The Microsoft updates released today are available in one big batch from Windows Update, or automagically via Automatic Updates. If you don’t have Automatic Updates enabled, please visit Windows Update sometime soon (click the Start/Windows button, then type Windows Update).

The newest Flash update from Adobe brings the player to v. 28.0.0.126 on Windows, Macintosh, Linux and Chrome OS. Windows users who browse the Web with anything other than Internet Explorer may need to apply the Flash patch twice, once with IE and again using the alternative browser (Firefox, Opera, e.g.).

Chrome and IE should auto-install the latest Flash version on browser restart (users may need to manually check for updates and/or restart the browser to get the latest Flash version). Chrome users may need to restart the browser to install or automatically download the latest version.

When in doubt, click the vertical three dot icon to the right of the URL bar, select “Help,” then “About Chrome”: If there is an update available, Chrome should install it then. Chrome will replace that three dot icon with an up-arrow inside of a circle when updates are waiting to be installed.

Standard disclaimer: Because Flash remains such a security risk, I continue to encourage readers to remove or hobble Flash Player unless and until it is needed for a specific site or purpose. More on that approach (as well as slightly less radical solutions ) can be found in A Month Without Adobe Flash Player. The short version is that you can probably get by without Flash installed and not miss it at all.

For readers still unwilling to cut the cord, there are half-measures that work almost as well. Fortunately, disabling Flash in Chrome is simple enough. Paste “chrome://settings/content” into a Chrome browser bar and then select “Flash” from the list of items. By default it should be set to “Ask first” before running Flash, although users also can disable Flash entirely here or whitelist and blacklist specific sites.

Another, perhaps less elegant, solution is to keep Flash installed in a browser that you don’t normally use, and then to only use that browser on sites that require it.

Not long ago, phishing attacks were fairly easy for the average Internet user to spot: Full of grammatical and spelling errors, and linking to phony bank or email logins at unencrypted (http:// vs. https://) Web pages. Increasingly, however, phishers are upping their game, polishing their copy and hosting scam pages over https:// connections — complete with the green lock icon in the browser address bar to make the fake sites appear more legitimate.

According to stats released this week by anti-phishing firm Phishlabs, nearly 25 percent of all phishing sites in the third quarter of this year were hosted on HTTPS domains — almost double the percentage seen in the previous quarter.

“A year ago, less than three percent of phish were hosted on websites using SSL certificates,” wrote Crane Hassold, the company’s threat intelligence manager. “Two years ago, this figure was less than one percent.”

As shown in the examples above (which KrebsOnSecurity found in just a few minutes of searching via phish site reporting service Phishtank.com), the most successful phishing sites tend to include not only their own SSL certificates but also a portion of the phished domain in the fake address.

Why are phishers more aggressively adopting HTTPS Web sites? Traditionally, many phishing pages are hosted on hacked, legitimate Web sites, in which case the attackers can leverage both the site’s good reputation and its SSL certificate.

Yet this, too, is changing, says Phishlabs’ Hassold.

“An analysis of Q3 HTTPS phishing attacks against PayPal and Apple, the two primary targets of these attacks, indicates that nearly three-quarters of HTTPS phishing sites targeting them were hosted on maliciously-registered domains rather than compromised websites, which is substantially higher than the overall global rate,” he wrote. “Based on data from 2016, slightly less than half of all phishing sites were hosted on domains registered by a threat actor.”

Hassold posits that more phishers are moving to HTTPS because it helps increase the likelihood that users will trust that the site is legitimate. After all, your average Internet user has been taught for years to simply “look for the lock icon” in the browser address bar as assurance that a site is safe.

Perhaps this once was useful advice, but if so its reliability has waned over the years. In November, Phishlabs conducted a poll to see how many people actually knew the meaning of the green padlock that is associated with HTTPS websites.

“More than 80% of the respondents believed the green lock indicated that a website was either legitimate and/or safe, neither of which is true,” he wrote.

What the green lock icon indicates is that the communication between your browser and the Web site in question is encrypted; it does little to ensure that you really are communicating with the site you believe you are visiting.

At a higher level, another reason phishers are more broadly adopting HTTPS is because more sites in general are using encryption: According to Let’s Encrypt, 65% of web pages loaded by Firefox in November used HTTPS, compared to 45% at the end of 2016.

Also, phishers no longer need to cough up a nominal fee each time they wish to obtain a new SSL certificate. Indeed, Let’s Encrypt now gives them away for free.

The major Web browser makers all work diligently to index and block known phishing sites, but you can’t count on the browser to save you:

So what can you do to make sure you’re not the next phishing victim?

Don’t take the bait: Most phishing attacks try to convince you that you need to act quickly to avoid some kind of loss, cost or pain, usually by clicking a link and “verifying” your account information, user name, password, etc. at a fake site. Emails that emphasize urgency should be always considered extremely suspect, and under no circumstances should you do anything suggested in the email.

Phishers count on spooking people into acting rashly because they know their scam sites have a finite lifetime; they may be shuttered at any moment. The best approach is to bookmark the sites that store your sensitive information; that way, if you receive an urgent communication that you’re unsure about, you can visit the site in question manually and log in that way. In general, it’s a bad idea to click on links in email.

Links Lie: You’re a sucker if you take links at face value. For example, this might look like a link to Bank of America, but I assure you it is not. To get an idea of where a link goes, hover over it with your mouse and then look in the bottom left corner of the browser window.

Yet, even this information often tells only part of the story, and some links can be trickier to decipher. For instance, many banks like to send links that include ridiculously long URLs which stretch far beyond the browser’s ability to show the entire thing when you hover over the link.

The most important part of a link is the “root” domain. To find that, look for the first slash (/) after the “http://” part, and then work backwards through the link until you reach the second dot; the part immediately to the right is the real domain to which that link will take you.

“From” Fields can be forged: Just because the message says in the “From:” field that it was sent by your bank doesn’t mean that it’s true. This information can be and frequently is forged.

If you want to discover who (or what) sent a message, you’ll need to examine the email’s “headers,” important data included in all email.  The headers contain a lot of information that can be overwhelming for the untrained eye, so they are often hidden by your email client or service provider, each of which may have different methods for letting users view or enable headers.

Describing succinctly how to read email headers with an eye toward thwarting spammers would require a separate tutorial, so I will link to a decent one already written at About.com. Just know that taking the time to learn how to read headers is a useful skill that is well worth the effort.

Keep in mind that phishing can take many forms: Why steal one set of login credentials for a single brand when you can steal them all? Increasingly, attackers are opting for approaches that allow them to install a password-snarfing Trojan that steals all of the sensitive data on victim PCs.

So be careful about clicking links, and don’t open attachments in emails you weren’t expecting, even if they appear to come from someone you know. Send a note back to the sender to verify the contents and that they really meant to send it. This step can be a pain, but I’m a stickler for it; I’ve been known to lecture people who send me press releases and other items as unrequested attachments.

If you didn’t go looking for it, don’t install it: Password stealing malware doesn’t only come via email; quite often, it is distributed as a Facebook video that claims you need a special “codec” to view the embedded content. There are tons of variations of this scam. The point to remember is: If it wasn’t your idea to install something from the get-go, don’t do it.

Lay traps: When you’ve mastered the basics above, consider setting traps for phishers, scammers and unscrupulous marketers. Some email providers — most notably Gmail — make this especially easy.

When you sign up at a site that requires an email address, think of a word or phrase that represents that site for you, and then add that with a “+” sign just to the left of the “@” sign in your email address. For example, if I were signing up at example.com, I might give my email address as krebsonsecurity+example@gmail.com. Then, I simply go back to Gmail and create a folder called “Example,” along with a new filter that sends any email addressed to that variation of my address to the Example folder.

That way, if anyone other than the company I gave this custom address to starts spamming or phishing it, that may be a clue that example.com shared my address with others (or that it got hacked!). I should note two caveats here. First, although this functionality is part of the email standard, not all email providers will recognize address variations like these. Also, many commercial Web sites freak out if they see anything other than numerals or letters, and may not permit the inclusion of a “+” sign in the email address field.