A well-designed antivirus utility ought to eliminate ransomware on sight, but ransomware designers are tricky. They work hard to get around both old-school signature-based malware detection and more flexible modern techniques. It only takes one slipup by your antivirus to let a new, unknown ransomware attack render your files unusable. Even if the antivirus gets an update that removes the ransomware, it can't bring back the files. Modern antivirus utilities supplement signature-based detection with some form of behavior monitoring. Some rely exclusively on watching for malicious behavior rather than looking for known threats. And behavior-based detection specifically aimed at encryption-related ransomware behaviors is becoming more common. Ransomware typically goes after files stored in common locations like the desktop and the Documents folder. Some antivirus tools and security suites foil ransomware attacks by denying unauthorized access to these locations. Typically, they pre-authorize known good programs such as word processors and spreadsheets. On any access attempt by an unknown program, they ask you, the user, whether to allow access. If that notification comes out of the blue, not from anything you did yourself, block it! Of course, using an online backup utility to keep an up-to-date backup of your essential files is the very best defense against ransomware. First, you root out the offending malware, perhaps with help from your antivirus company's tech support. With that task complete, you simply restore your backed-up files. Note that some ransomware attempts to encrypt your backups as well. Backup systems in which your backed-up files appear in a virtual disk drive may be especially vulnerable. Check with your backup provider to find out what defenses the product has against ransomware.