To carry out illicit acts, cybercriminals use various kinds of malicious software, generically known as malware. Malware is malicious code used to steal data, bypass access controls, or damage or compromise systems. Knowing the various types of malware and how they spread is essential to detecting and removing them.
Spyware: spyware is designed to track and spy on users' online activity. It can, for example, log every keystroke, take screenshots, and capture sensitive data, including online banking details. It does this by altering the device's security settings. One example is Pegasus, the spyware developed by Israel's NSO Group.
Adware: adware, usually installed alongside other software, aims to automatically display advertisements, often through web browsers. Characterized by intrusive pop-up ads, this threat can come bundled with spyware.
Backdoor: this security flaw allows unauthorized access, bypassing normal authentication procedures. Hackers can thus access a system and send it remote commands. Operating in the background, backdoors are particularly hard to detect.
Ransomware: ransomware encrypts data or systems, making them inaccessible until a ransom is paid. It often spreads via phishing emails or by exploiting software vulnerabilities. A well-known example is WannaCry, which in 2017 hit thousands of computers worldwide.
Scareware: uses intimidation tactics to trick the user into taking specific actions. It typically simulates system warnings, reporting nonexistent security threats, and induces the user to install malware.
Rootkit: this malware modifies the operating system to create a backdoor, allowing remote access. It exploits software vulnerabilities and makes detection difficult by modifying system files and monitoring tools. Removing it often requires reinstalling the operating system.
Virus: a virus is a program that replicates and attaches itself to other files, altering their code. It requires human interaction to activate and can be programmed to trigger at specific times. Some viruses are harmless, others highly damaging. They spread via USB devices, email and shared networks.
Trojan: this malware hides malicious operations behind a legitimate-looking appearance. It doesn't replicate on its own, but serves as a Trojan horse to introduce other malware. It's often found in media files or games.
Worm: worms replicate on their own to spread between computers. They don't need a host program to activate. They exploit system vulnerabilities and can cause significant damage. A historic example is the Code Red worm, which in 2001 infected over 300,000 servers in 19 hours.