Phone numbers stink for security and authentication. They stink because most of us have so much invested in these digits that they’ve become de facto identities. At the same time, when you lose control over a phone number — maybe it’s hijacked by fraudsters, you got separated or divorced, or you were way late on your phone bill payments — whoever inherits that number can then be you in a lot of places online.

How exactly did we get to the point where a single, semi-public and occasionally transient data point like a phone number can unlock access to such a large part of our online experience? KrebsOnSecurity spoke about this at length with Allison Nixon, director of security research at New York City-based cyber intelligence firm Flashpoint.

Nixon said much of her perspective on mobile identity is colored by the lens of her work, which has her identifying some of the biggest criminals involved in hijacking phone numbers via SIM swapping attacks. Illegal SIM swaps allow fraudsters to hijack a target’s phone’s number and use it to steal financial data, passwords, cryptocurrencies and other items of value from victims.

Nixon said countless companies have essentially built their customer authentication around the phone number, and that a great many sites still let users reset their passwords with nothing more than a one-time code texted to a phone number on the account. In this attack, the fraudster doesn’t need to know the victim’s password to hijack the account: He just needs to have access to the target’s mobile phone number.

“As a consumer, I’m forced to use my phone number as an identity document, because sometimes that’s the only way to do business with a site online,” Nixon said. “But from that site’s side, when they see a password reset come in via that phone number, they have no way to know if that’s me. And there’s nothing anyone can do to stop it except to stop using phone numbers as identity documents.”

Beyond SIM-swapping attacks, there are a number of ways that phone numbers can get transferred to new owners, Nixon said. The biggest reason is lack of payment for past phone bills. But maybe someone goes through a nasty divorce or separation, and can no longer access their phone or phone accounts. The account is sent to collections and closed, and the phone number gets released back into the general pool for reassignment after a period of time.

Many major providers still let people reset their passwords with just a text message. Last week I went to regain access to a Yahoo account I hadn’t used in almost five years. Yahoo’s forgot password feature let me enter a phone number, and after entering a code sent to my phone I was able to read my email.

So, if that Yahoo account is tied to a mobile number that you can receive text messages at, then you can assume control over the account. And every other account associated with that Yahoo account. Even if that phone number no longer belongs to the person who originally established the email account.

This is exactly what happened recently to a reader who shared this account:

A while ago I bought a new phone number. I went on Yahoo! mail and typed in the phone number in the login. It asked me if I wanted to receive an SMS to gain access. I said yes, and it sent me a verification key or access code via SMS. I typed the code I received. I was surprised that I didn’t access my own email, but the email I accessed was actually the email of the previous owner of my new number.

Yahoo! didn’t even ask me to type the email address, or the first and last name. It simply sent me the SMS, I typed the code I received, and without asking me to type an email or first and last name, it gave me access to the email of my number’s PREVIOUS OWNER. Didn’t ask for credentials or email address. This seriously needs to be revised. At minimum Yahoo! should ask me to type the email address or the first and last name before sending me an SMS which contains an access code.

Brian Krebs (BK): You have your own experiences like this. Or sort of. You tell.

Allison Nixon (AN): Any threat intelligence company will have some kind of business function that requires purchasing burner phones fairly frequently, which involves getting new phone numbers. When you get new numbers, they are recycled from previous owners because there probably aren’t any new ones anymore. I get a lot of various text messages for password resets. One I kept getting was texts from this guy’s bank. Every time he got a deposit, I would get a text saying how much was deposited and some basic information about the account.

I approached the bank because I was concerned that maybe this random person would be endangered by the security research we were going to be doing with this new number. I asked them to take him off the number, but they said there wasn’t anything they could do about it.

One time I accidentally hijacked a random person’s account. I was trying to get my own account back at an online service provider, and I put a burner phone number into the site, went through the SMS password reset process, got the link and it said ‘Welcome Back’ to some username I didn’t know. Then I clicked okay and was suddenly reading the private messages of the account.

I realized I’d hijacked the account of the previous owner of the phone. It was unintentional, but also very clear that there was no technical reason I couldn’t hijack even more accounts associated with this number. This is a problem affecting a ton of service providers. This could have happened at many, many other web sites.

BK: We weren’t always so tied to our phone numbers, right? What happened?

AN: The whole concept of a phone number goes back over a hundred years. The operator would punch in a number you know was associated with your friend and you could call that person and talk to them. Back then, a phone wasn’t tied any one person’s identity, and possession of that phone number never proved that person’s identity.

But these days, phone number are tied to peoples’ identities, even though we’re recycling them and this recycling is a fundamental part of how the phone system works. Despite the fact that phone number recycling has always existed, we still have all these Internet companies who’ve decided they’re going to accept the phone number as an identity document and that’s terrible.

BK: How does the phone number compare to more traditional, physical identity documents?

AN: Take the traditional concept of identity documents — where you have to physically show up and present ID at some type of business or office, and then from there they would look up your account and you can conduct a transaction. Online, it’s totally different and you can’t physically show your ID and can’t show your face.

In the Internet ecosystem, there are different companies and services that sell things online who have settled on various factors that are considered a good enough proxy for an identity document. You supply a username, password, and sometimes you provide your email address or phone number. Often times when you set up your account you have some kind of agreed-upon way of proofing that over time. Based on that pre-established protocol, the user can log in and do transactions.

It’s not a good system and the way the whole thing works just enables fraud. When you’re bottlenecked into physically showing up in a place, there’s only so much fraud you can do. A lot of attacks against phone companies are not attacking the inherent value of a phone number, but its use as an identity document.

BK: You said phone number recycling is a fundamental part of how the phone system works. Talk more about that, how common that is.

AN: You could be divorced, or thrown into sudden poverty after losing a job. But that number can be given away, and if it goes to someone else you don’t get it back. There all kinds of life situations where a phone number is not a good identifier.

Maybe part of the reason the whole phone number recycling issue doesn’t get much attention is people who can’t pay their bills probably don’t have a lot of money to steal anyways, but it’s pretty terrible that this situation can be abused to kick people when they’re down. I don’t think a lot of money can be stolen in this way, but I do think the fact that this happens really can undermine the entire system.

BK: It seems to me that it would be a good thing if more online merchants made it easier to log in to their sites without using passwords, but instead with an app that just asks hey was that you just now trying to log in? Yes? Okay. Boom, you’re logged in. Seems like this kind of “push” login can leverage the user’s smart phone while not relying on the number — or passwords, for that matter.

If phone numbers are bad, what should we look to as more reliable and resilient identifiers?

AN: That’s something I’ve been thinking a lot about lately. It seems like all of the other options are either bad or really controversial. On the one hand, I want my bank to know who I am, and I want to expose my email and phone number to them so they can verify it’s me and know how to get in touch with me if needed. But if I’m setting up an email account, I don’t want to have to give them all of my information. I’m not attached to any one alternative idea, I just don’t like what we’re doing now.

For more on what you can do to reduce your dependence on mobile phone numbers, check out the “What Can You Do?” section of Hanging Up on Mobile in the Name of Security.

Online advertising firm Sizmek Inc. [NASDAQ: SZMK] says it is investigating a security incident in which a hacker was reselling access to a user account with the ability to modify ads and analytics for a number of big-name advertisers.

In a recent posting to a Russian-language cybercrime forum, an individual who’s been known to sell access to hacked online accounts kicked off an auction for “the admin panel of a big American ad platform.”

“You can add new users to the ad system, edit existing ones and ad offers,” the seller wrote. The starting bid was $800.

The seller included several screen shots of the ad company’s user panel. A few minutes on LinkedIn showed that many of these people are current or former employees of Sizmek.

The seller also shared a screenshot of the ad network’s Alexa site rankings:

I checked Sizmek’s Alexa page and at the time it almost mirrored the statistics shown in the screenshot above. Sizmek’s own marketing boilerplate says the company operates its ad platform in more than 70 countries, connecting more than 20,000 advertisers and 3,600 agencies to audiences around the world. The company is listed by market analysis firm Datanyze.com as the world third-largest ad server network.

After reaching out to a number of folks at Sizmek, I heard back from George Pappachen, the company’s general counsel.

Pappachen said the account being resold on the dark web is a regular user account (not a all-powerful administrator account, despite the seller’s claim) for its Sizmek Advertising Suite (SAS). Pappachen described Sizmek’s SAS product line as “a sizable and important one” for the company and a relatively new platform that has hundreds of users.

He acknowledged that the purloined account had the ability to add or modify the advertising creatives that get run on customer ad campaigns. And Sizmek is used in ad campaigns for some of the biggest brands out there. Some of the companies shown in the screenshot of the panel shared by the dark web seller include PR firm Fleishman-Hillard, media giants Fox Broadcasting, Gannett, and Hearst Digital, as well as Kohler, and Pandora.

Crooks who exploited this access could hijack existing ad campaigns running on some of the world’s top online properties, by inserting malicious scripts into the HTML code of ads that run on popular sites. Or they could hijack referral commissions destined for others and otherwise siphon ad profits from the system.

“Or someone who is looking to sabotage our systems in a bigger way or allow malicious code to enter our systems,” Pappachen offered.

Pappachen said Sizmek forced a password reset on all internal employees (“a few hundred”), and that the company is scrubbing its SAS user database for departed employees, partners and vendors whose accounts may have been hijacked.

“We’re now doing some level of screening to see if there’s been any kind of intrusion we can detect,” Pappachen said. “It seemed like [the screenshots were accounts from] past employees. I think there were even a couple of vendors that had access to the system previously.”

The Sizmek incident carries a few lessons. For starters, it seems like an awful lot of people at Sizmek had access to sensitive controls and data a good deal longer than they should have. User inventory and management is a sometimes painful but very necessary ongoing security process at any mature organization.

Best practices in this space call for actively monitoring all accounts — users and admins — for signs of misuse or unauthorized access. And when employees or vendors sever business ties, terminate their access immediately.

Pappachen asked KrebsOnSecurity what else could have prevented this. I suggested some form of mobile-based multi-factor authentication option would prevent stolen credentials from turning into instant access. He said the company does use app/mobile based authentication for several of its new products and some internal programs, but allowed that “the legacy ones probably did not have this feature.”

PASSWORD SPRAYING

It’s not clear how this miscreant got access to Sizmek’s systems. But it is clear that attackers have moved rapidly of late toward targeting employees at key roles in companies they’d like to infiltrate, and they’re automating the guessing of passwords for employee accounts. One popular version of this attack involves what’s known as “password spraying,” which attempts to access a large number of accounts (usernames/email addresses) with a few commonly used passwords.

There are technologies like CAPTCHAs — requiring the user to solve an image challenge or retype squiggly letters — which try to weed out automated bot programs from humans. Then again, password spraying attacks often are conducted “low and slow” to help evade these types of bot challenges.

Password spraying was suspected in a compromise reported last week at Citrix, which said it heard from the FBI on March 6 that attackers had successfully compromised multiple Citrix employee accounts. A little-known security company Resecurity claimed it had evidence that Iranian hackers were responsible, had been in Citrix’s network for years, and had offloaded terabytes of data.

Resecurity drew criticism from many in the security community for not sharing enough evidence of the attacks. But earlier this week the company updated its blog post to include several Internet addresses and proxies it says the attackers used in the Citrix campaign. The update stated the attackers had gained access to nearly 32,000 Citrix accounts through password spraying.

Resecurity also presented evidence that it notified Citrix of the breach as early as Dec. 28, 2018. Citrix initially denied that claim, but has since acknowledged that it did receive a notification from Resecurity on Dec. 28. Citrix has declined to comment further beyond saying it is still investigating the matter.

BRUTE-FORCE LIGHT

If anything, password spraying is a fairly crude, if sometimes marginally effective attack tool. But what we’ve started to see more of over the past year has been what one might call “brute-force light” attacks on accounts. A source who has visibility into a botnet of Internet of Things devices that is being mostly used for credential stuffing attacks said he’s seeing the attackers use distributed, hacked systems like routers, security cameras and digital video recorders to anonymize their repeated queries.

This source noticed that the automated system used by the IoT botmasters typically will try several dozen variations on a password that each target had previously used at another site — adding a “1” or an exclamation point at the end of a password, or capitalizing the first letter of whole words in previous passwords, and so on.

The idea behind this method to snare not only users who are wholesale re-using the same password across multiple sites, but to also catch users who may just be re-using slight variations on the same password.

This form of credential stuffing is brilliant from the attacker’s perspective because it probably nets him quite a few more correct guesses than normal password spraying techniques.

It’s also smart because it borrows from human nature. Let’s say your average password re-user is in the habit of recycling the password “monkeybutt.” But then he gets to a site that wants him to use capitalization in his password to create an account. So what does this user pick? Yes, “Monkeybutt.” Or “Monkeybutt1”. You get the picture.

There’s an old saying in security: “Everyone gets penetration tested, whether or not they pay someone for the pleasure.” It’s kind of like that with companies and their users and passwords. How would your organization hold up to a password spraying or brute-force light attack? If you don’t know, you should probably find out, and then act on the results accordingly. I guarantee you the bad guys are going to find out even if you don’t.

Microsoft on Tuesday pushed out software updates to fix more than five dozen security vulnerabilities in its Windows operating systems, Internet Explorer, Edge, Office and Sharepoint. If you (ab)use Microsoft products, it’s time once again to start thinking about getting your patches on. Malware or bad guys can remotely exploit roughly one-quarter of the flaws fixed in today’s patch batch without any help from users.

One interesting patch from Microsoft this week comes in response to a zero-day vulnerability (CVE-2019-0797) reported by researchers at Kaspersky Lab, who discovered the bug could be (and is being) exploited to install malicious software.

Microsoft also addressed a zero day flaw (CVE-2019-0808) in Windows 7 and Windows Server 2008 that’s been abused in conjunction with a previously unknown weakness (CVE-2019-5786) in Google’s Chrome browser. A security alert from Google last week said attackers were chaining the Windows and Chrome vulnerabilities to drop malicious code onto vulnerable systems.

If you use Chrome, take a moment to make sure you have this update and that there isn’t an arrow to the right of your Chrome address bar signifying the availability of new update. If there is, close out and restart the browser; it should restore whatever windows you have open on restart.

This is the third month in row Microsoft has released patches to fix high-severity, critical flaws in the Windows component responsible for assigning Internet addresses to host computers (a.k.a. “Windows DHCP client”).

These are severe “receive a bad packet of data and get owned” type vulnerabilities. But Allan Liska, senior solutions architect at security firm Recorded Future, says DHCP vulnerabilities are often difficult to take advantage of, and the access needed to do so generally means there are easier ways to deploy malware.

The bulk of the remaining critical bugs fixed this month reside in Internet Explorer, Edge and Office. All told, not the craziest Patch Tuesday. Even Adobe’s given us a month off (or at least a week) patching critical Flash Player bugs: The Flash player update shipped this week includes non-security updates.

Staying up-to-date on Windows patches is good. Updating only after you’ve backed up your important data and files is even better. A good backup means you’re not pulling your hair out if the odd buggy patch causes problems booting the system.

Windows 10 likes to install patches all in one go and reboot your computer on its own schedule. Microsoft doesn’t make it easy for Windows 10 users to change this setting, but it is possible. For all other Windows OS users, if you’d rather be alerted to new updates when they’re available so you can choose when to install them, there’s a setting for that in Windows Update.

As always, if you experience any problems installing any of these patches this month, please feel free to leave a comment about it below; there’s a good chance other readers have experienced the same and may even chime in here with some helpful tips.

Further reading:

Qualys

SANS Internet Storm Center

Ask Woody

ZDNet

Very often the most clever component of your typical ATM skimming attack is the hidden pinhole camera used to record customers entering their PINs. These little video bandits can be hidden 100 different ways, but they’re frequently disguised as ATM security features — such as an extra PIN pad privacy cover, or an all-in-one skimmer over the green flashing card acceptance slot at the ATM.

And sometimes, the scammers just hijack the security camera built into the ATM itself.

Below is the hidden back-end of a skimmer found last month placed over top of the customer-facing security camera at a drive-up bank ATM in Hurst, Texas. The camera components (shown below in green and red) were angled toward the cash’s machine’s PIN pad to record victims entering their PINs. Wish I had a picture of this thing attached to the ATM.

The clever PIN grabber was paired with an “insert skimmer,” a wafer-thin, usually metallic and battery powered skimmer made to be fitted straight into the mouth of the ATM’s card acceptance slot, so that the card skimmer cannot be seen from outside of the compromised ATM.

For reference, here’s a similar card acceptance slot, minus the skimmer.

Police in Hurst, Texas released a photo taken from footage showing what appears to be a young woman affixing the camera skimmer to the drive-up ATM. They said she was driving a blue Ford Expedition with silver trim on the lower portion of the vehicle.

The skimmer crooks seem to realize that far fewer people are going to cover their hand when entering a PIN at drive-up ATMs. Often the machine is either too high or too low for the driver-side window, and covering the PIN pad to guard against hidden cameras can be a difficult reach for a lot of people.

Nevertheless, covering the PIN pad with a hand, wallet or purse while you enter the PIN is one of the easiest ways to block skimming attacks. The skimmer scammers don’t just want your bank card: They want your PIN so they can create an exact copy of the card and use it at another ATM to empty your checking or savings account.

So don’t be like the parade of people in these videos from hidden cameras at hacked ATMs who never once covered the PIN pad.

Further reading: Woman Caught on Video Installing Skimmer Outside Bank’s ATM in Hurst

Most people who have frozen their credit files with Equifax have been issued a numeric Personal Identification Number (PIN) which is supposed to be required before a freeze can be lifted or thawed. Unfortunately, if you don’t already have an account at the credit bureau’s new myEquifax portal, it may be simple for identity thieves to lift an existing credit freeze at Equifax and bypass the PIN armed with little more than your, name, Social Security number and birthday.

Consumers in every U.S. state can now freeze their credit files for free with Equifax and two other major bureaus (Trans Union and Experian). A freeze makes it much harder for identity thieves to open new lines of credit in your name.

In the wake of Equifax’s epic 2017 data breach impacting some 148 million Americans, many people did freeze their credit files at the big three in response. But Equifax has changed a few things since then.

Seeking to manage my own credit freeze at equifax.com as I’d done in years past, I was steered toward creating an account at myequifax.com, which I was shocked to find I did previously possess.

Getting an account at myequifax.com was easy. In fact, it was too easy. The portal asked me for an email address and suggested a longish, randomized password, which I accepted. I chose an old email address that I knew wasn’t directly tied to my real-life identity.

The next page asked me enter my SSN and date of birth, and to share a phone number (sharing was optional, so I didn’t). SSN and DOB data is widely available for sale in the cybercrime underground on almost all U.S. citizens. This has been the reality for years, and was so well before Equifax announced its big 2017 breach.

myEquifax said it couldn’t verify that my email address belonged to the Brian Krebs at that SSN and DOB. It then asked a series of four security questions — so-called “knowledge-based authentication” or KBA questions designed to see if I can about my recent financial history.

In general, the data being asked about in these KBA quizzes is culled from public records, meaning that this information likely is publicly available in some form — either digitally or in-person. Indeed, I have long assailed the KBA industry as creating a false sense of security that is easily bypassed by fraudsters.

One potential problem with relying on KBA questions to authenticate consumers online is that so much of the information needed to successfully guess the answers to those multiple-choice questions is now indexed or exposed by search engines, social networks and third-party services online — both criminal and commercial.

The first three multiple-guess questions myEquifax asked were about loans or debts that I have never owed. Thus, the answer to the first three KBA questions asked was, “none of the above.” The final question asked for the name of our last mortgage company. Again, information that is not hard to find.

Satisfied with my answers, Equifax informed me that yes indeed I was Brian Krebs and that I could now manage my existing freeze with the company. After requesting a thaw, I was brought to a vintage Equifax page that looked nothing like myEquifax’s sunnier new online plumage.

This page informed me that if I previously secured a freeze of my credit file with Equifax and been given a PIN needed to undo that status in any way, that I should be ready to provide said information if I was requesting changes via phone or email. 

In other words, credit freezes and thaws requested via myExquifax don’t require users to supply any pre-existing PIN.

Fine, I said. Let’s do this.

myEquifax then asked for the date range requested to thaw my credit freeze. Submit.

“We’ve successfully processed your security freeze request!,” the site declared.

This also was exclaimed in an email to the random old address I’d used at myEquifax, although the site never once made any attempt to validate that I had access to this inbox, something that could be done by simply sending a confirmation link that needs to be clicked to activate the account.

In addition, I noticed Equifax added my old mobile number to my account, even though I never supplied this information and was not using this phone when I created the myEquifax account.

myEquifax.com does not currently seek to verify the account by requesting confirmation via a phone call or text to the phone number associated with the account (also, recall that even providing a phone number was optional).

Happily, I did discover then when I used a different computer and Internet address to try to open up another account under my name, date of birth and SSN, it informed me that a profile already existed for this information. This suggests that signing up at myEquifax is probably a good idea, given that the alternative is more risky.

It was way too easy to create my account, but I’m not saying everyone will be able to create one online. In testing with several readers over the past 24 hours, myEquifax seems to be returning a lot more error pages at the KBA stage of the process now, prompting people to try again later or make a request via email or phone.

Equifax spokesperson Nancy Bistritz-Balkan said not requiring a PIN for people with existing freezes was by design.

“With myEquifax, we created an online experience that enables consumers to securely and conveniently manage security freezes and fraud alerts,” Bistritz-Balkan said..

“We deployed an experience that embraces both security standards (using a multi-factor and layered approach to verify the consumer’s identity) and reflects specific consumer feedback on managing security freezes and fraud alerts online without the use of a PIN,” she continued. “The account set-up process, which involves the creation of a username and password, relies on both user inputs and other factors to securely establish, verify, and authenticate that the consumer’s identity is connected to the consumer every time.”

I asked Bistritz-Balkan what else besides a username and a password the company may have meant by “multi-factor;” I’m still waiting for clarification. But I did not experience anything like multi-factor in setting up or logging into my myEquifax account.

This may by closer to Equifax’s idea of multi-factor: The company told me that if I still really wanted to use my freeze PIN, I could always call their 800 number (800-349-9960) or make the request via mail. Nevermind that if I’m a bad guy looking to hack others, I’m definitely going to be using the myEquifax Web site — not the options that make me have to supply a PIN.

Virtually the entire United States population in 2017 became eligible for free credit monitoring from Equifax following its 2017 breach. Credit monitoring can be useful for recovering from identity theft, but consumers should not expect these services to block new account fraud; the most they will likely do in this case is alert you after ID thieves have already opened new accounts in your name.

A credit freeze does not impact your ability to use any existing financial accounts you may have, including bank and credit/debit accounts. Nor will it protect you from fraud on those existing accounts. It is mainly a way to minimize the risk that someone may be able to create new accounts in your name.

If you haven’t done so lately, it might a good time to order a free copy of your credit report from annualcreditreport.com. This service entitles each consumer one free copy of their credit report annual from each of the three credit bureaus — either all at once or spread out over the year.

Additional reading:

Credit Freezes are Free: Let the Ice Age Begin

Plant Your Flag, Mark Your Territory

Experian Site Can Give Anyone Your Freeze PIN

Survey: Americans Spent $1.4B on Credit Freeze Fees in Wake of Equifax Breach

Equifax Breach Fallout: Your Salary History

Data Broker Giants Hacked by ID Theft Service

Experian Sold Access to ID Theft Service