To increase awareness of the very popular "Glee" TV show, Sky used its Twitter account @gleeonsky and paying for the hashtag #gleeonsky to be promoted to British Twitter users.

Spam accounts have been set up specifically for the purpose of distributing messages containing popular hashtags, in this case '#gleeonsky', to encourage curious users to click on malicious links.

Graham Cluley, senior technology consultant at Sophos said that promoting hastags on Twitter and making it a trending topic can cost companies considerable amounts of money, He said that on Twitter, spammers don't care if their accounts get reported and shut down by Twitter security, because they can just create further accounts. The process can be entirely automated, meaning that malicious or offensive links can continue to be spread without human effort.

"Even if a hashtag or a tweet is sponsored, Twitter users should be wary about clicking on unknown links, just as they would in their inbox," Cluely said.

"In this instance, most of the spammed Tweets are claiming to link to sites containing illicit celebrity photos, but the spammers can choose to redirect users to any webpage they choose once they've clicked on a link.  It could be a phishing site designed to steal Twitter credentials, it could be a fake pharmacy, it could be an explicit or offensive site, or it could be a website harbouring malware."