Crack tools are often detected as malware or viruses, and for good reason. By definition, they are designed to modify programs and files so that they do not work as intended. This can include deleting verification files, modifying the registry, and other measures to prevent the target from functioning properly. For instance, if you're an avid Xbox Live player, attempting to use cracked games is a risky endeavor. Crack software is also classified as adware, as it delivers advertising content to the user and can be considered an invasion of privacy.
However, sometimes the people who make cracks available for download (hosters) will infect them with additional Trojans or spyware components. The older the version of the software you are using, the greater the risk of malware exploiting any vulnerabilities in the decrypted software. It is possible for decrypted software to contain malware, as well as social engineering techniques used by hackers to gain access to those who download it. It is not feasible for anyone to reverse engineer every single crack on the market, which is why it is often assumed that there is malware present in pirated software. Two of the most common approaches to implementing cracks are highly suspicious activities that could cause antivirus (AV) software to think that a crack is a virus.
According to anecdotal reports from Avast, cracked games may still work properly, but with an added invisible threat. Antiviruses detect cracks because they may contain malware, the decrypted code triggers a false positive, and because antivirus companies are actively fighting against piracy - especially in enterprise antivirus software - through heuristic or signature-based detection. In some cases, security software does not need to analyze suspicious features or behavior to detect cracks. It is not uncommon for known harmless crack signatures to be permanently blacklisted by antivirus software, even if those cracks do not infect your devices or collect personal information. If you're ever unsure about a crack you've downloaded, you can try running it in a sandbox or using an online service like FireAMP to analyze what files and logs are created. However, often there will be nothing suspicious.
Additionally, those who manage the software may want to know that decrypted software has been installed on their machine. When downloading a Remote Access Trojan (RAT) in its decrypted form, it's important to take a moment and consider why someone would give away something that requires so much patience and knowledge to decrypt - a process that can take hours or even days.