Actualy, the security issues here are easy to deal with. Use the normalized screenname, not the formatted screenname. A little bit of background: In AIM scrennnames, only alphnumerics are significant, and those are case-insignificant. You can change the case and spacing, and add extra chacaters, to scrennnames at any time (there's somthing under file/preferences to do it in WinAIM, IIRC, or under tools/protocol actions in GAIAM). Thus, when comparing or storing scrennames for long terms, you should use the normalized name, which is defined as $sn=lc $sn; s/[^a-z0-9]//g, more or less. Naturaly falling out of this is that normalized screen names are always valid filenames on any reasonable platform (which doesn't include plain old DOS, in which filenames are too short -- IIRC SNs now have a limit of 18 or so chars in normal form.)