The Spam Act 2003, which covers some types of email and phone spam. Email "spam" is unsolicited bulk email. There was also Cloudmark spam and phishing protection and Trend Micro antivirus. It ranges from email spam to online scams. Facebook and Twitter are not immune to messages containing spam links. It is also used to circumvent email screening and spam filtering. Online advertising began with unsolicited bulk e-mail advertising known as "e-mail spam". This prevents text-based spam filters from detecting and blocking spam messages. Multiple posting can also be used as a method of trolling or spreading forum spam. RX Limited advertised its services through spam email. Occasionally, unmoderated review systems are abused to send flames, spam, or trolling messages. Backscatter is a side-effect of email spam, viruses, and worms. A low number of false negatives is an indicator of the efficiency of spam filtering. A spambot is a computer program designed to assist in the sending of spam. Newsgroups tend to be poorly organized and flooded with content that is off-topic or spam.