Hackers can use a backdoor to install all manner of malware on your computer.
- Spyware is a type of malware that, once deployed on your system, collects information about you, the sites you visit on the Internet, the things you download, the files you open, usernames, passwords, and anything else of value. A lesser form of spyware called keyloggers specifically track every keystroke and click you make. Companies may use spyware/keyloggers as a legitimate and legal, means of monitoring employees at work.
- Ransomware is a type of malware designed to encrypt your files and lock down your computer. In order to get back those precious photos, documents, etc. (or whatever file type the attackers choose to target) you have to pay the attackers via some form of cryptocurrency, usually Bitcoin.
- Use your computer in a DDoS attack. Using the backdoor to get super user access on your system, cybercriminals can take command of your computer remotely, enlisting it in a network of hacked computers, aka a botnet. With this zombie computer botnet, criminals can then overwhelm a website or network with traffic from the botnet in what's known as a distributed denial of service attack (DDoS). The flood of traffic prevents the website or network from responding to legitimate requests, effectively taking the site out of service.
- Cryptojacking malware is designed to use your system's resources to mine cryptocurrency. In short, every time someone exchanges cryptocurrency the transaction is recorded on an encrypted virtual ledger known as the blockchain. Cryptomining is the process of validating these online transactions in exchange for more cryptocurrency and it takes an enormous amount of computing power. Instead of buying the expensive hardware required for cryptomining, criminals have found that they can simply enlist hacked computers in a botnet that works the same as expensive cryptomining farms.