Original URL: http://www.theregister.co.uk/2006/08/08/phishing_trojan/
Phishing Trojan plays ping-pong with captured data
Hide and seek
Security researchers have identified a new Trojan which sends data back to attackers via an unconventional communications protocol (for malware) in a bid to escape detection.
The as-yet unnamed phishing Trojan transmits stolen information back to hackers via ICMP (Internet Control Message Protocol) packets instead of email or HTTP packets, the standard route for transmitting purloined information.
After infecting a victim's computer, the Trojan is programmed to install itself as an Internet Explorer Browser Helper Object (BHO). The software then waits for a victim to post sensitive data online. This data, once entered, is captured by the Trojan and sent to attackers.
Instead of using email or HTTP POST requests, the Trojan encodes purloined data using a simple XOR algorithm before placing it into the data section of an ICMP ping packet.
"To network administrators and egress filters, this ICMP packet looks like legitimate traffic leaving the network. However, the ICMP packet actually contains encoded personal information entered by a user. The attackers presumably capture this packet at their remote server, where the packet is easily decoded to reveal the information entered by the user," reports  web security firm Websense, which analysed the behaviour of the Trojan after being among the first to receive samples of the malware code. ®