Messaging spam

[4] Many IM services are publicly linked to social media platforms, which may include information on the user such as age, sex, location and interests.

Advertisers and scammers can gather this information, sign on to the service, and send unsolicited messages which could contain scam links, pornographic material, malware or ransomware.

Often if the user responds they receive a URL inviting them to a private livestream that will ask them to enter credit card details for "age verification".

[citation needed] In an opinion based recommender system, an important concern is how to evaluate the user-generated reviews on the items.

However, even if a review is well generated, they can still be harmful to the recommender system by their biased prejudice to form an actual advertisement or slander towards a target item.