networking spam such as that generated by the social networking site Quechup. Instant messaging Instant messaging spam makes use of instant messaging systems. Although less prevalent than its e-mail counterpart, according to a report from Ferris Research, 500 million spam IMs were sent in 2003, twice the level of 2002. Newsgroup and forum Newsgroup spam is a type of spam where the targets are Usenet newsgroups. Spamming of Usenet newsgroups actually pre-dates e-mail spam. Usenet convention defines spamming as excessive multiple posting, that is, the repeated posting of a message (or substantially similar messages). The prevalence of Usenet spam led to the development of the Breidbart Index as an objective measure of a message's "spamminess". Forum spam is the creation of advertising messages on Internet forums. It is generally done by automated spambots. Most forum spam consists of links to external sites, with the dual goals of increasing search engine visibility in highly competitive areas such as weight loss, pharmaceuticals, gambling, pornography, real estate or loans, and generating more traffic for these commercial websites. Some of these links contain code to track the spambot's identity; if a sale goes through, the spammer behind the spambot earns a commission. Mobile phone Mobile phone spam is directed at the text messaging service of a mobile phone. This can be especially irritating to customers not only for the inconvenience, but also because of the fee they may be charged per text message received in some markets. To comply with CAN-SPAM regulations in the US, SMS messages now must provide options of HELP and STOP, the latter to end communication with the advertiser via SMS altogether. Despite the high number of phone users, there has not been so much phone spam, because there is a charge for sending SMS. Recently, there are also observations of mobile phone spam delivered via browser push notifications. These can be a result of allowing websites which are malicious or delivering malicious ads to send a user notifications. Social networking spam Facebook and Twitter are not immune to messages containing spam links. Spammers hack into accounts and send false links under the guise of a user's trusted contacts such as friends and family. As for Twitter, spammers gain credibility by following verified accounts such as that of Lady Gaga; when that account owner follows the spammer back, it legitimizes the spammer. Twitter has studied what interest structures allow their