### Comment:
How can malware infect a computer without the user's knowledge?

### REPLY:
Malware can infect a computer without the user's knowledge through various techniques. One method is through social engineering, where attackers deceive users into clicking on a malicious link or opening a malicious attachment. Exploit kits can also be used to take advantage of software vulnerabilities and silently install malware. Drive-by downloads, where malware is automatically downloaded when visiting a compromised website, can also occur without the user's knowledge. Additionally, attackers can use fileless malware that resides only in memory, leaving no traces on the infected computer's hard drive.