What is a 'Backdoor'

A backdoor is a way in which a third party can access software or a computer system without authentication in order to gain access and/or monitor that system. Also called a trap door, the term can also be applied to the way in which hackers or government agencies gain illicit access to computer systems. 


Backdoors can be a threat to user security and privacy and are difficult to unmask because they are designed to elude detection. They also offer a variety of ways to access a user’s system. Firewalls, monitoring networks for suspicious activity, and preventing open source programs from accessing a network can help protect against backdoor intrusion.

Not all backdoors are illicit. Backdoors can be set up by network administrators as a way to gain access to a system in order to monitor and administer it remotely. These portals can be protected with a username and password that can't be changed. But some of these backdoors, which are typically built into the system, can make them susceptible to hacking. In these cases, they may install malware or other kinds of software or programs to alter your files or steal your data. 

Android's Pre-Installed Backdoors

In November 2016, security analysts discovered that more than 100,000 Android phones contained a pre-installed backdoor that sent users’ locations, text messages, call logs and contact lists to recipients in China for an unknown purpose, without the phone users’ knowledge. Users would not have been able to detect the transmissions even if they had known about them because of how backdoors work. Backdoors can also be used by the government and federal agencies that want to monitor cellphone behavior, including tracking internet use and monitoring conversations.

Governments Agencies Using Backdoors

In the 1990s, the U.S. National Security Agency (NSA) publicly campaigned to insert a backdoor in all encrypted communications online to allow it to eavesdrop. One of the arguments against allowing the NSA to do this is that backdoors create vulnerabilities that can be exploited by more than just the entity that installed the backdoor. Enemies of the United States could exploit the same backdoors that the NSA wanted to use. The agency ended up using other methods, such as hacking and weakening encryption standards, to accomplish its goals. The NSA also worked with providers such as Microsoft to gain pre-encrypted access to popular consumer services like email, online storage and Internet phone calls and chats.

Backdoor access was at the heart of a fight between the FBI and Apple after the 2015 shootings in San Bernardino. Opponents argued that allowing such access would not be an isolated incident but would set a new precedent that would reverse much of the progress made in internet security and allow governments to have backdoor access to other internet and computer-based systems ranging from cars to thermostats. The precedent could also have allowed other law enforcement agencies, from the U.S. Department of Justice (DOJ) to local police departments, to gain access to people’s phones. The case was withdrawn by the federal government after the FBI announced it was able to unlock one of the shooter's iPhones

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