A strain of attacks that appear to target Pakistani nationals. We named the attack “BITTER” based on the network communication header used by the latest variant of remote access tool (RAT) used.
Spear-phishing emails are used to target prospective BITTER victims. The campaign predominantly used the older, relatively popular Microsoft Office exploit, CVE-2012-0158, in order to download and execute a RAT binary from a website. Below is an example of a spear-phishing email they used earlier this month. The recipient is an individual from a government branch in Pakistan, while the sender purports to be coming from another government branch of Pakistan.
In one instance, they used a RAR SFX dropper that drops both their RAT and a picture of a Pakistani woman as a decoy. A quick Google image search on the dropped picture indicates that the picture was grabbed from Pakistani dating sites.
BITTER used RATs that are compiled using Microsoft Visual C++ 8.0. They use a few iterations of their RAT with the main difference being the RAT’s command and control (C2) communication method. Earlier variants communicated to its C2 via an unencrypted HTTP POST. Below is an example of an older variant’s phone home request:
Newer ones, on the other hand, use encrypted TCP connection such as the one shown in the introduction above. Both older and newer variants are used simultaneously today in the campaign.
The RAT version (SHA1 d7a770233848f42c5e1d5f4b88472f7cb12d5f3d) that they used in their latest campaign is capable of executing the following backdoor capabilities, essentially allowing the attackers to gain full remote control over a victim’s PC.
In addition, the vast majority of their RAT binaries contained the following digital signature with a non-trusted CA Root certificate:
Malware Hash (MD5/SHA1/SH256)