A backdoor is a type of infection where the creator or distributor secretly creates a method of accessing the device or website remotely, avoiding normal authentication. Backdoors allow the attacker to access a system continuously without being noticed. This is considered an extremely serious type of infection.
Backdoors can not only lead to the theft of data, including financial and personal information but also provides an attacker with a continuous means to install more malware. This is frequently the case, where an attacker installs a backdoor only to use it as a gateway for installing other viruses. In some situations, especially at the enterprise level, an attacker will install a backdoor and then lapse activity for an extended period of time before proceeding with their attack. For the attacker, this reduces their chances of being caught. In turn, it becomes more likely that even if the malware installed at a later date is removed, the backdoor will not be detected and they will be able to execute more attacks in the future. Backdoors can accidentally be downloaded from e-mail attachments or bundled with other software. Vulnerabilities in third-party applications may also allow the malware to be installed.
Backdoors can be extremely difficult to detect and remove from the system. Changing passwords and login information will not necessarily help, as backdoors traditionally bypass login information rather than steal it. It is nearly impossible for most users to manually remove a backdoor, but strong anti-virus software may be better suited to detect and remove them. Keeping your computer or website up to date can also help defend against backdoors, as it is often vulnerabilities in the operating system, plugins and themes that allow a backdoor to thrive. If a device or website is infected with a backdoor and other attempts to remove it appear to have failed, it may be necessary to reformat the hard drive and install a copy of the operating system from scratch. It is extremely important to ensure any files recovered onto a system from backup do not themselves contain malware.
Just as backdoors can allow other malware to be installed, certain types of malware can also initiate a backdoor. With that nature, this type of infection tends to have a compounding effect on the system, making it of the most devastating forms of malware.
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