A persistent security assault by someone trying to gain restricted access by altering data. There are multiple techniques, decryption for example, which can be used to lead the attack.

An attack which results in an unauthorized state change, such as the manipulation of files, or the adding of unauthorized files.

Attacks which modify the target system or message, i.e. attacks which violate the integrity of the system or message are examples of an active attack. Another example in this category is an attack on the availability of a system or service, a so-called denial-of-service (DoS) attack.