Malware
malicious software · virus · worm · spyware · rootkit · drive-by download · watering hole · logiciel malveillant
Any program designed to cause harm: stealing data, spying, encrypting or destroying files, or taking control of a device without its user knowing.
In practice
The word covers many families: viruses (which attach to files) and worms (which spread on their own from machine to machine through a flaw), Trojans (disguised as legitimate software), ransomware, infostealers, spyware (which silently watches what you type and do) and rootkits (which hide deep in the system to conceal the attacker and survive clean-ups). Most arrive through a malicious attachment or link, pirated software, a USB stick or an unpatched flaw, or simply by visiting a compromised page with an outdated browser (a drive-by download); attackers may even booby-trap a site their targets are known to visit (a watering hole). The most dangerous ones stay quiet for a long time, which is why behaviour-based detection matters more than antivirus signatures alone.
In June 2017, NotPetya spread through a booby-trapped update of a Ukrainian accounting package, then moved through networks on its own by stealing credentials and exploiting Windows flaws. It posed as ransomware but behaved like a wiper: even victims who paid could not get their files back.
How to protect yourself
- Keep systems and software up to date, starting with anything exposed to the internet.
- Deploy EDR on laptops and servers, and make sure someone acts on its alerts.
- Ban unapproved software and the everyday use of administrator accounts.
- Keep offline backups and test restoring them regularly.
