Updated Dyre, Dropped by Office Macros

Whenever attackers make a shift in tactics, techniques, and protocol (TTP), we like to make note of it to help both customers and the rest of the Internet community. We recently analyzed a sample that started out appearing to be Dridex, but quickly turned into a headache leading to Dyre that featured some notable differences to past Dyre samples. One PhishMe user was targeted to their personal account, and here’s a copy of the phishing email:

Figure 1 -- Phishing email

Figure 1 — Phishing email

Once opened, we’re presented with the very familiar story of “please enable this macro so you can get infected”. This time, they do give a few more instructions to the user, saying that the data is “encoded” and macros need to be enabled to read the text.

Detecting a Dridex Variant that Evades Anti-virus

Attackers constantly tweak their malware to avoid detection. The latest iteration of Dridex we’ve analyzed provides a great example of malware designed to evade anti-virus, sandboxing, and other detection technologies.

How did we get our hands on malware that went undetected by A/V? Since this malware (like the majority of malware) was delivered via a phishing email, we received the sample from a user reporting the phishing email using Reporter.

Dridex Code Breaking – Modify the Malware to Bypass the VM Bypass

Post Updated on March 25

The arrival of spring brings many good things, but it’s also prime season for tax-themed phishing emails. A partner of ours recently reported an email with the subject “Your Tax rebate” that contained an attachment with Dridex and password-protected macros to hinder analysis. If you read this blog, this story should sound familiar, but this particular strain took new precautions, such as adding a longer password and using VM detection inside of the code.

Dridex – Password Bypass, Extracting Macros, and Rot13

When attackers decide to password protect something, it can be very frustrating as an analyst, because we are often left with few options to find out what they are protecting. If this happens, we can always try to straight up brute force the password, but unless the attackers use something like 1q2w3e4r, we’re up a creek without an oar. If it’s an MD5 hash of a password, we have many more options to crack it. In the case of xls files, we have the option to essentially “wipe out” the password and give it our own password. In a recent wave of Dridex phishing emails, this is what we saw. Here’s the phishing email sent to one PhishMe employee: