I was wondering does Avast! check thru 3rd Party Chat Programs such as My!Chat, Cheetachat, or YahELite? ???
Instant Messagers that are not supported via Instant Messager provider are checked with Standard Shield.
If the ‘High’ sensibility level of protection is set 
Next days, version 4.5 will be released and the new list of IM applications supported will be: AIM (AOL Instant Messenger), Gadu-Gadu*, gaim*, ICQ, Miranda*, mIRC*, MSN/Windows Messenger, Odigo*, Psi Jabber Client*, Trillian, Yahoo! Messenger.
Protection of the programs marked by an asterisk (*) is available on Windows NT, 2000, XP, and 2003 only.