Botnets: How to fight the ever-growing threat on a technical level

Today's malware, short term for malicious software, poses one of the major threats to all currently operated computer systems. The scale of the problem becomes obvious by looking at the global economic loss caused by different kinds of malware, which is estimated to be more than US$10 billion every year. This particularly applies for botnets, which are a special kind of malware. In contrast to other kinds of malware, botnets utilize a hidden communication channel to receive commands from their operator and communicate their current status. The ability to execute almost arbitrary commands on the infected machines makes botnets a general-purpose tool to perform malicious cyber-activities. In this context, botnets are used for example by individual perpetrators, organized crime as well as governmentally supported organizations, in order to achieve individual gains. This chapter gives a technical insight into current botnet techniques and discusses state of the art countermeasures to combat the botnet threat in detail. This includes new detection methods as well as different approaches to actively compromise running botnets. Different techniques as well as their impact on current botnets are discussed, considering individual involved stakeholders. In addition to the technical countermeasures, current initiatives countering botnets are introduced.