Amnesty's U.K. website appears to have been cleaned as of Friday, but the Gh0st RAT variant used in this attack still has a low antivirus detection rate, Leonard said.

In order to protect themselves from such Web-based exploitation attacks, also known as drive-by downloads, users should keep their computer software up to date, especially the browser plug-ins. Website owners should also make sure that the software used on their websites, including its plug-ins, is current, and should harden their Web server environments in order to prevent infection, Leonard said.