Friday, January 31, 2014

Yahoo reveals coordinated attack on Yahoo Emails - encourages Password reset

On January 30, 2014, Jay Rossiter, the Senior Vice President for Yahoo's Platforms and Personalization Products shared An Important Security Update for Yahoo Mail Users on the companies Tumblr blog. In this time when "breach" is the biggest buzzword on the Internet, let's look at what the post is saying and is not saying and consider what we can learn and what we should do as a result of this information.

(click image to visit Yahoo! blogpost)

Is Yahoo a breach victim? or a champion?

(Quote): Recently, we identified a coordinated effort to gain unauthorized access to Yahoo Mail accounts.(/Quote)

While we don't know how they discovered this, the typical methods for discover would be some form of network analytics showing single IP addresses or sessions attempting to access multiple Yahoo email accounts in rapid succession, or, based on the keyword "effort", possibly attempting and failing generating a large number of password guesses. Like most Email Service Providers, Yahoo! retains records of which IP addresses have previously succeeded to access your email account, and a sudden spike in "wrong address / wrong device / wrong geography" alerts may be part of what led to the conclusion this was a coordinated effort.

While everyone is raging at Yahoo!, I believe that in this situation Yahoo! is providing a well-intentioned public service that actually reveals a pro-security stance in the company, NOT a weak security status! Read on to see why.

Password Re-Use is the Problem

Next, where did the data come from and what type of data was it?

(Quote): Based on our current findings, the list of usernames and passwords that were used to execute the attack was likely collected from a third-party database compromise. We have no evidence that they were obtained directly from Yahoo's systems.(/Quote)

On face value many are jumping to the conclusion that this indicates that Yahoo! is allowing some third party to store userids and passwords of Yahoo! users on their systems. Again, as an outsider sharing my reasoning on this event, I don't believe that is what is being said. PASSWORD RE-USE IS REACHING CRISIS LEVELS!. Oops? Did I scream that? I guess I did! The problem that I believe we are dealing with here is that many systems on the Internet ask you to use your EMAIL ADDRESS as your UserID on their system. This is a great convenience in many ways, however, in this case, it also means that a criminal now can associate your userid on one system in a very direct way to your userid on your email provider's system. MORE THAN 81 MILLION AMERICANS (and more than 200 Million people worldwide) still use a Yahoo! email account! This means that in any breach on any system where your userid is equal to your email account, there is a very great chance that the primary accounts found in that breach would be Yahoo email accounts. Despite repeated warnings, most users still use the same password on ALL of their systems. Because of this, it is logical for a criminal who obtains userids and passwords from ANY source to try those same userids and passwords at Yahoo against the matching email account.

What is the Criminals' End-Game?

(Quote): The information sought in the attack seems to be names and email addresses from the affected accounts’ most recent sent emails.(/Quote)

If someone is using the same userid and password on multiple systems, it is likely they are doing so on many ADDITIONAL systems as well. By reading the recent emails found in the Inbox and Sent mail, the criminals are likely able to determine other places where the Yahoo email user has additional accounts. For example, when I make a purchase on,, or pay my credit card bill at or what happens? They send a confirmation of my purchase (or my statement) to my email account. If a criminal knew that information, they would be able to then try that same Yahoo email account as the userid and password and attempt to access those other accounts. In addition, how do ALL of those service confirm a password reset account? Through an email message with a "click to change your password" link. Since the criminal now has control of your Yahoo account, even if you DID use a different password, they can now reset it at will!

Of course there is also the possibility that they are just after "London traveler" type scams where knowledge of the individuals in your address book is used to send personal pleas for financial assistance due to some type of crisis. We've covered those types of scams since at least 2009 in this blog. The more recent social engineering attacks that we've heard of have been searching the compromised accounts for evidence of communications with bankers and then using the knowledge of the previous conversation to ask for financial favors or skirting of the rules to help perform a financial transaction via email.

How is Yahoo Protecting their Customers?

This is from their letter, but it is exactly what I would hope they would do after detecting this situation!

  • We are resetting passwords on impacted accounts and we are using second sign-in verification to allow users to re-secure their accounts. Impacted users will be prompted (if not, already) to change their password and may receive an email notification or an SMS text if they have added a mobile number to their account.
  • We are working with federal law enforcement to find and prosecute the perpetrators responsible for this attack.
  • We have implemented additional measures to block attacks against Yahoo’s systems.
Jay Rossiter is also trying to help educate Yahoo! users by recommending this page of suggestions for Safeguarding your Yahoo account. Whether you are a Yahoo! user, a Gmail user, a user, or whether you are just using your corporate email account, the advice given there is well worth reviewing and following.

In the Safeguarding Your Yahoo! Account document, I'd like to call special attention to their recommendation to having an alternative email and mobile phone on file with Yahoo. This isn't so they can violate your privacy. It is so they can better protect your account! I've used this service myself from Yahoo within the past two weeks and was very pleased that they texted a password reset code to my cell phone before allowing a password change request to continue.

High praise to Yahoo! for recommending that you enable a mobile-phone based password reset. I wish my banks and credit card issuers would require the same! This isn't an example of Yahoo! being a security victim, but being a security LEADER! It is shameful that my Yahoo! email account is better protected than many other accounts! (Test your own accounts: Can you click an "I Forgot My Password" link on your bank/electronics/music website to reset your password by email? )

Breaches, Phishing, It doesn't matter ... DO NOT RE-USE PASSWORDS!

At Malcovery Security we specialize in email-based Threat Intelligence. Part of that practice is having an enormous database of spam and phishing information, including nearly 700,000 confirmed phishing websites and information about each of those threats. Many of the malware samples that we report on daily through our "Today's Top Threats" report will also steal userids and passwords to accounts, including your email accounts. Almost every version of Zeus will do so, as one example. Here are a few of the Yahoo-targeted phishing scams that were popular during the previous week:

  • BT Internet Phish:

    In this long-running phishing campaign, users of Yahoo's "" email domain are told that BT Broadband (formerly British Telecom) is discontinuing their email account and will replace it with a Premium Email account that they have to pay for, unless they confirm they want to keep the account by entering their email userid and password to prove they are really in control of the account.

    (This phishing screenshot was captured by Malcovery January 23, 2014 from dtinternet[.]bug3[.]com)

  • Google Docs Phish:

    Although this phish claims to be from Google Docs, this scam campaign began its life as a ReMax realty phish. In order to confirm your identity, you are asked to provide the userid and password of whichever popular email service you are using. From there the threats are similar to those described above.

    (This phishing screenshot was captured by Malcovery January 29, 2014 from www[.]thewigleygroup[.]com/googledocss/sss/)

  • GT Bank / Yahoo! Phish:

    GT Bank is Guaranty Trust Bank plc, a pan-African bank with Nigerian roots. In this example, the phishing target is actually Yahoo, but since the phish was created by someone logging in from Africa, the Yahoo! page they captured is adorned with a GTBank logo and advertisement.

    (This particular phishing screenshot was captured by Malcovery January 22, 2014 from highbeam[.]co[.]th/eart/Indezx.html)

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