Malware
Malware authors target bugs, or loopholes, to exploit. A common method is exploitation of a buffer overrun vulnerability, where software designed to store data in a specified region of memory does not prevent more data than the buffer can accommodate being supplied. Malware may provide data that overflows the buffer, with malicious executable code or data after the end; when this payload is accessed it does what the attacker, not the legitimate software, determines.
Linux malware
As of 2018 there had not yet been a single widespread Linux virus or malware infection of the type that is common on Microsoft Windows; this is attributable generally to the malware's lack of root access and fast updates to most Linux vulnerabilities.