Hackers have planted malware on the British Communist Party's website, says Sophos.

According to the security firm a Microsoft Silverlight script on the website was altered to allow a malicious JavaScript code to be executed.

"The Communist Party's website infection is invisible to the naked eye, but buried inside the code of a plugin for their webpages," said Graham Cluley, senior technology consultant for Sophos.

"The code is designed to deliver funky animation and video effects to website visitors - but actually tries to invisibly download malicious code from web servers based in China and Russia."

Cluely said that the hacker may not have targeted the website because of its political nature but that web users should still be wary of compromised websites.

"All computer users need to learn that it's not just adult and gambling websites that are dangerous - any website, if not properly secured, can fall victim and leave you seeing red."