Backdoors are features or programs that can be used to evade the security features of a program, device, portal, or service.
A feature in a program, device, portal or service can be a backdoor if its design or implementation introduces a security risk. For example, hardcoded administrator access to an online portal can be used as a backdoor.
Backdoors usually take advantage of flaws in the code of a program, device, portal, or service. The flaws may be bugs, vulnerabilities or undocumented features.
Attackers use backdoors to gain unauthorized access or to perform harmful actions that allow them to evade security features such as access restrictions, authentication or encryption.