Malware
Malware (a portmanteau for malicious software) is any software intentionally designed to cause damage to a computer, server, client, or computer network. Malware does the damage after it is implanted or introduced in some way into a target's computer and can take the form of executable code, scripts, active content, and other software. The code is described as computer viruses, worms, Trojan horses, ransomware, spyware, adware, and scareware, among other terms. Malware has a malicious intent, acting against the interest of the computer user—and so does not include software that causes unintentional harm due to some deficiency, which is typically described as a software bug.
Mahdi (malware)
Mahdi is computer malware that was initially discovered in February 2012 and was reported in July of that year. According to Kaspersky Lab and Seculert (an Israeli security firm which discovered the malware), the software has been used for targeted cyber espionage since December 2011, infecting at least 800 computers in Iran and other Middle Eastern countries. Mahdi is named after files used in the malware and refers to the Muslim figure.