Botnets are posing a serious threat to our online society. At the end of 2016, one such botnet caused a wave of destruction, knocking a lot of services offline. Many people don’t realize there were quite a few significant botnets over the course of history. This trend dates back all the way to early 2004 when Bagle became the first “major” botnet that sent out billions of spam messages every day.

#4 Marina Botnet

Around the same time Bagle was sending spam messages all over the world, the Marina Botnet quickly made a name for itself. With over 6 million bots pumping out spam emails every single day, it became apparent these “hacker tools” could get out of hand very quickly. At its peak, Marina Botnet delivered 92 billion spam emails per day. It was also known under different names, including Cotmonger, BOB dc, and Kraken.

#3 Conficker

The name Conficker will ring a bell for most people, as this botnet caught the world by storm in November of 2008. A total of 10.5 million computers and other devices were part of this massive botnet, as it grew at an unprecedented pace. Thankfully, this botnet was never used to perform DDoS attacks – as far as we know – otherwise it would have caused significant damage.

#2 Mariposa

Between the end of 2008 and December 2009, Mariposa made a fair few media headlines. The second-largest botnet recorded to date – according to Wikipedia – was eventually shut down by the FBI and other international law enforcement agencies. Its most famous feat was infecting computers of over half of the Fortune 1,000 companies at that time.

As one would expect, the malware used to enslave computers was spread to P2P networks, MSN links, and infected USB devices. Compromised machines would see keyloggers and banking trojans installed on the hard drive in quick succession. Mariposa was one of the first botnets to be “rented out” to other cyber criminals. The “leader’ behind the Mariposa botnet was tracked down as he failed to use a VPN while connecting to the botnet’s command and control server during the FBI investigation.

#1 BredoLab

BredoLab is by far the largest recorded botnet to date, as it combined the resources of over 30 million computers around the world. Russian hackers set up this malicious network to conduct viral email spam. Thankfully, law enforcement agencies managed to bring the network down in November of 2010, after they seized the command and control servers.

This particular botnet sent out a lot of emails containing malware-laden attachments. Opening this attachment turned the computer into an infected host, and also created a backdoor for hackers to download other malicious software on the computer. Large parts of the botnet were leased to third parties, and it is estimated the BredoLab owner made up to US$139,000 per month.

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