Social networking site Facebook is being overwhelmed by rogue third-party applications designed to harvest user log-in credentials and spam 'friends' in order to drive ad revenue for the creators.

The first application was spotted on Monday by Trend Micro senior security advisor Rik Ferguson, and another five have since appeared, all following the same format and with the same intent.

Facebook managed to shut down these apps but, at the time of writing, Ferguson claimed that more had appeared, taking the total into double digits.

"The new rogue apps have slightly more credible notifications to your friends and also now feature bogus notifications to the profile owner, presumably in an effort to persuade the victim to install further apps and maximise the fraudsters' advertising returns," he wrote in a blog post.

Although the apps pose no threat to data held on a user's PC, they are breaking Facebook guidelines and can cause irritation for users as they spam the victim's 'friends'.

Ferguson warned users to be extra vigilant if they are asked to install third-party apps.

"My advice is only install applications which actually give you functionality you want. Don't install everything just because someone sends you a notification," he said.

"When you get a notification from an application, there should be written 'block' in small text underneath. If you click on this you'll never be bothered by that app again."