Which passive attack technique involves infecting frequently visited websites with malware?

The correct answer is the watering hole attack technique. This approach involves targeting specific groups of users by compromising websites that those users frequently visit. The attacker infects these trusted sites with malware, which may not be recognized as malicious by users due to the site’s established reputation.

When a victim visits the compromised site, the malware can exploit vulnerabilities in the user’s system or browser, allowing the attacker to gain unauthorized access or deliver harmful payloads. This method is subtle because the attack leverages the victim's trust in the legitimate site, making it an effective way to bypass security measures that users may have in place for unfamiliar or less trustworthy sites.

Other options like social networking, typosquatting, and pretexting involve different techniques for executing attacks. Social networking often involves deceiving individuals through fake profiles or social engineering rather than targeting websites. Typosquatting relies on creating similar domain names to trap users who make typographical errors, and pretexting involves creating a fabricated scenario to engage a target and extract information. These do not specifically encompass the technique of infecting legitimate websites with malware that the watering hole attack embodies.