Out of the 5,000 bots I just checked via my access logs, none used the user_agent xpymep.exe
Most bots I detected have user agents like:
"Mozilla/5.0 (Windows NT 5.2; rv:12.0) Gecko/20100101 Firefox/12.0"
"Mozilla/5.0 (Windows NT 6.1; rv:13.0) Gecko/20100101 Firefox/13.0"
"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.5 (KHTML, like Gecko) Chrome/19.0.1084.52 Safari/536.5"
(these were confirmed bots ... making their selves appear as browsers)
<< Obviously don't ban these, you might find it reduces your bots... but you exclude quite a few humans too
but it cant do any harm to give the other ones ago.