The banking password and information stealer Clampi recently was described as infecting anywhere from 100,000 and 1 million windows PC’s. Let’s take a closer look at this menace, and what interesting Clampi behaviors ThreatFire has been preventing in our community.
First, let’s talk about the distribution over the past year. Most of the Clampi executables appear to be unique, and appear to have been run on no more than one machine. The bulk of these executables are repacked and re-obfuscated to evade AV solutions, so only a quarter of the Clampi malware prevented in the ThreatFire community over the past year showed up on more than one system. Mostly all of the Clampi variants seen on multiple user desktops appear to have been delivered via an Adobe Acrobat client-side exploit. As posted previously about mainstream Windows pdf readers, be sure to update the software on your system, especially popular web browser third party plugins. A high number of these Clampi-delivering exploits successfully attacked Acrobat 7.0. Unfortunately, while the message may be getting out that third party plugins need to be updated on a regular basis, the advice does not seem to be followed reliably.
The trojan runs a new instance of Internet Explorer and injects it with executable code of its own, accesses the personal store of saved passwords, and phones the data off of the system to multiple web sites. It’s not a set of new malicious techniques, but highly problematic nonetheless. ThreatFire prevents these behaviors reliably, and PC Tools AV reliably detects the malware with one of several heuristic routines: Trojan.DL.Ilomo.Gen!Pac, Trojan.DR.Ilomo.Gen!Pac.2, Trojan.DL.Ilomo.Gen!Pac .
Symantec named this malware Trojan.Clampi, and it has been labelled inconsistently by other groups with a handful of other names, including Clomp, Downloader, Inject, Rscan, Small, Ilomo, Agent2, Agent, and often it is detected by its packer’s characteristics. Unfortunately, its packer changes and old signatures can become ineffective against this malware as it appears on systems around the world over time. PCTAV heuristics were effective over time, however.
Update: Please see post with a bit of technical information regarding Clampi variant’s injection technique.