‘Botnet’ refers to a group of computers whose security has been compromised in order to use them as ‘zombies’ to send spam e-mail messages or to attack servers. These botnets are created by ‘bots’, malicious programs that turn individual computers into ‘zombies’ which can be remotely controlled by the attacker via a ‘bot-herder’ command and control server. Botnets are one of the more dangerous types of menace which occur in cyberspace, as they can harm whole networks as well as individual computers. In addition to sending spam emails, botnets are used to distribute adware and spyware as well. They can also be used to perform ‘Denial of Service (DoS)’ and ‘Distributed Denial of Service (DDoS)’ attacks on servers, during which zombie computers are used to overload target servers with requests, causing the server to freeze from excessive information.
Botnets enter user systems via Trojans or viruses which carry the botnet’s code as the payload. These Trojans and viruses may be delivered to the user in the form of spam emails or they could get downloaded from malicious websites, posing as essential video and audio codecs. Once installed, the botnet immediately connects to the bot-herder server and receives instructions such as where to send its spam emails, which servers to attack and instructions on how to propagate the botnet across the internet. Most of a botnet’s activity occurs without the user noticing any major difference in their computer; therefore it is important that users have a clear understanding of how to recognize a botnet infection.
The first sign that your computer is infected with a botnet is the inevitable slowing down of your computer. Your internet connection will also slow down drastically due to the many connections being maintained by the botnet program. There will also be an inexplicable loss of hard disk space as well as your browser will be compromised. In other words, your browser will close unexpectedly, its homepage will be irreversibly changed, and your desktop will be inexplicably changed.
If you notice these symptoms, your computer is most probably infected with a botnet. You should immediately take steps to remove it, either by following an online guide specific to the botnet installed on your computer, or by using a web-based repair service or a legitimate antivirus program.