This week we discovered a large malware spam campaign that used the Zbot Trojan executable. It started with a Voice Message/MMS Service spam message yesterday at around 3:30AM GMT.
The spam uses any of the following subject lines:
- T-Mobile MMS Service
- Vodafone Voice Message
- Vodafone MMS Service
- Orange Voice Message
- T-Mobile Voice Message
- Orange MMS Service
The HOTFIX "Important SystemUpdate" spam campaign followed at around 6:00AM GMT. The email claims to be from various anti-virus companies urging the users to install the attached "system patch".
The subject lines used by this spam campaign:
- AVG Anti-Virus Free Edition: Important System Update - requires immediate action
- AVG Internet Security 2012: Important System Update - requires immediate action
- AntiVir Desktop: Important System Update - requires immediate action
- Avast Antivirus: Important System Update - requires immediate action
- Avira Desktop: Important System Update - requires immediate action
- Baidu Antivirus: Important System Update - requires immediate action
- Cloud Antivirus Firewall: Important System Update - requires immediate action
- ESET NOD32 Antivirus: Important System Update - requires immediate action
- Kaspersky Anti-Virus: Important System Update - requires immediate action
- McAfee Personal Firewall: Important System Update - requires immediate action
- McAfee VirusScan Enterprise: Important System Update - requires immediate action
- Microsoft Security Essentials: Important System Update - requires immediate action
- Norton 360: Important System Update - requires immediate action
- Norton AntiVirus: Important System Update - requires immediate action
- Norton Internet Security: Important System Update - requires immediate action
- Symantec Endpoint Protection: Important System Update - requires immediate action
- Trend Micro Titanium Internet Security: Important System Update - requires immediate action
- Windows Defender: Important System Update - requires immediate action
A third spam campaign followed suit, this time using the subject line format, "DHL Delivery Status #[10 hexadecimal char]".
Our spamtrap timeline shows a sudden peak of activity involving these spam campaigns, and then just as suddenly, a decrease. This shows how quick a spammer can change their spam campaign over time.
These three spam campaigns were sent by the same botnet that we suspect is a variant of a Cutwail spambot. The attached files are an executable of a Zeus variant. It copies itself to the %appdata% directory then injects itself into Explorer.exe. It also adds an autorun registry to execute itself on Windows startup. Once installed in a victim's machine, the Zeus Trojan acts as a client that receives commands from its command-and-control server. The botnet operator can then send instructions such as sniffing a user's bank transaction. Our detailed analysis of the Zeus Trojan can be found in this page.
Trustwave's Secure Email Gateway customers were protected from this spam campaign without any additional action required.
