I have heard people talking about a yahoo messenger invisible hack, which in essence consists in a 3rd party sniffing tool that hacks the Yahoo IM network and detects the real connection status of a user.
I would like to warn my readers from using 3rd party tools to probe the Yahoo IM network. Those 3rd party sniffing tools compromise your privacy, as they can potentially open “back doors” to your system and have your personal information and data stolen.
If for emergency reasons still need to know how to know whether a contact of yours is online, although his/her connection status is offline, you can use one of the following two methods:
Using the Yahoo Conference settings
1. Open a conversation with your contact.
2. Click the Conference button. The Conference window will open up.
3. Click the Invite button. If the Talk button is highlighted, then your contact is online, if not he/ she’s offline.
Using the Yahoo Doodle IMvironment
1. Open a conversation with your contact.
2. Click the IMvironment button.
3. Select See all IMvironments then pick Yahoo! tools and Doodle.
4. If you see the following screen, then your contact is offline, if the screen is blank he is actually online:
