Amnesty International’s UK website was hacked to host the dangerous Gh0st RAT Trojan for two days this week, security firm Websense has revealed.

Attacking browsers unpatched against the common CVE-2012-0507 Java vulnerability (also used by the Mac Flashback Trojan), between 8 and 9 May visitors would have been at risk of downloading a Windows executable hiding behind a valid VeriSign-issued digital certificate.

Anyone clicking Ok to this install trick would have become infected with Gh0st RAT, a potent backdoor Trojan used to cull passwords and files and just about anything else the attacker wants to take from the infected system.

The injected web code was removed after Websense alerted Amnesty to the issue.

The attack bears all the hallmarks of a series of attacks that appear to be targeting pro-Tibet organisations and sympathisers, most likely by a group connected to China.

In March, Gh0st RAT was part of the ‘ByShe’ attack aimed at the Central Tibet Administration and International Campaign for Tibet using a malicious Word attachment. That attack also exploited a VeriSign-issued digital certificate, on that occasion one that had been revoked.

The certificate used in the latest Amnesty attack was issued to a Chinese Shenzen-based company, while Gh0st RAT itself is associated with the active Chinese GhostNet hacking group.

“Exploit kits zoom in on vulnerable websites, even ones with good intentions,” said Websense Security Labs senior manager, Carl Leonard. “This compromise is more serious than your average. With a low AV detection rate, Gh0st RAT is a powerful tool that allows backdoor access into infected machines.”

Last week Websense reported that the National Security Studies (INSS) website had been compromised using the same CVE-2012-0507 Java vulnerability to serve the Poison Ivy Trojan, a relative of Gh0st RAT with the same data-stealing design.

The lesson, as always, is not to install anything unexpected, closing a browser process manually if presented with a Windows User Account Control message that seems suspicious.

Browsers should always be carefully patched, including plug-ins for commonly-targeted software such as Java and Flash.