Linux-based IRCBot spotted in the wild
The Dell SonicWALL Threats Research team has spotted a Trojan which targets the Linux platform. Tsunami is an IRC bot which uses its victim's machine to perform Denial of Service attacks. This Trojan has been around since at least 2002 and was previously been ported from Linux to OS X and now appears to be making a come back.
This Trojan arrives as a packed ELF file with symbols and debugging information stripped.
The malware author has changed all references to UPX in its strings to prevent tools from identifying the packer and from decompressing it.
This was probably done to make reversing challenging for the malware analyst. The author even left a message in its strings.
Upon execution The Trojan makes the following DNS query:
It then connects to an IRC server and waits for further instructions.
Below are some of the system calls executed when debugged using strace:
In order to start after reboot, the Trojan adds itself to cron.
* * * * * /home/test/malware > /dev/null 2>&1 &
It adds a lock file to identify whether the file is already running
During our analysis, we have seen it trying to establish SSH connections to random servers which appears to be attempts to brutefoce the logins.
Since we added a signature to detect this variant of Tsunami Trojan, we have observed an increasing amount of firewall hits based on our statistics below:
Dell SonicWALL Gateway AntiVirus provides protection against this threat with the following signature:
- GAV: Tsunami.BT (Trojan)