malware that essentially is a form of social engineering
Malware Trojan horses are generally spread by some form of social engineering, for example where a user is duped into executing an e-mail attachment disguised to be unsuspicious, (e.g., a routine form to be filled in), or by drive-by download. Although their payload can be anything, many modern forms act as a backdoor, contacting a controller which can then have unauthorized access to the affected computer.[26] While Trojan horses and backdoors are not easily detectable by themselves, computers may appear to run slower due to heavy processor or network usage.