Security researchers from Sophos warn that the type of survey-themed spam that has become all too common on Facebook in recent months is now also targeting YouTube users via personal messages.

Sophos Senior Technology Consultant Graham Cluley provides an example of such spam that was recently received on the company's YouTube account.

In the rather lengthy personal message the senders make significant efforts to persuade the recipient into visiting an external link.

In order to capture the user's attention, the spam starts by praising their videos and voice and offers tips on how to get more views.

In the message the spammers are open about the fact that accessing the promised information involves taking a survey and even go on to recommend one that might seem enjoyable.

While at first glance these surveys might look harmless, users should be aware that they collect personal information, which is later used in targeted advertising campaigns.

Furthermore, many of them try to sign up people to premium rate services and the high charges involved are always hidden away in the fine print.

Survey-themed scams are becoming increasingly prevalent on social networking websites because they represent a profitable business model.

Through complex affiliate marketing schemes the spammers earn a commission for every user who signs up to one of the presented offers and this creates a vicious circle.

The more users land on these pages, the more money the spammers win, which in turn compels them to generate even more spam.

"It doesn't matter if you receive a message via Facebook, YouTube or traditional email - you should always be suspicious of unsolicited communications and think before you click," Graham Cluley advises.

Also, when confronted with offers that seem irresistible it's best to keep in mind the old saying: "If it sounds too good to be true, it probably is."