I wonder what do you want the malware to see? and why? do you expect the malware to behave differently if you send them different error messages?
The purpose is to report to the user the kind of Malware he or she is using. For me it helps to identify the malware, too, which we have to uninstall.
Since the request is blocked there is no logging any more in the useragent_log file. So I have to look to the computer and identify the software manually...
Regards, Alexander