Malware may recruit the IT systems of an organisation into botnets. Attackers, who often control thousands of systems in a botnet, can use them to send spam or start distributed denial-of-service (DDoS) attacks on third parties. Even though the affected organisation itself may not be damaged directly, this may have negative effects regarding the availability and integrity of its own services and IT systems, and may even result in legal problems. For example, if an organisation's e-mail server is blacklisted, it may no longer be possible to send and receive e-mails.