I have had several incidents where I found someone was reading my IM's between my girlfriend and myself, on Yahoo, of course. I have also had these listeners pop into my convos, overiding the convo as well, and say things to me, or to my girlfriend. It looks like the message comes from my girlfriend, with the persons name immediately following hers.
Eg: "Girlfriend:personxxx: whatever they say to me".
This is taking place in "real time", and these people are also able to access my Yahoo buddy list as well, and who knows what else. How is this being done, is my real question, and is whatever program they are using available?
BTW- I am not a computer wizard/expert/programmer, etc, and the people doing this are not either. But I do find it disconcerting to know my conversations can be read by a third party at will.
My guess is you have a backdoor (http://en.wikipedia....oor_(computing)) or trojan (http://en.wikipedia....rse_(computing)) installed on your system that is completely independent of Yahoo! Messenger. These types of programs are usually distributed via email or an attachment sent to you in Messenger. If you can remember a strange program that was sent to you and then the computer started acting funny then you have your culprit.
The best fix is to reformat your hard drive and reinstall the operating system from a known good source. Some may say that this is overkill but you do not know how advanced the attacker is so every precaution should be taken. In some cases there may be a rootkit (http://en.wikipedia.org/wiki/Rootkit) installed and no matter what you do the only solution is to reformat. Even if you don’t have a backdoor to you system (my guess is very unlikely) a reformat should still be done and a new copy of Yahoo! Messenger installed.
If you are a novice user;
• First check to make sure you have a copy of your operating system such as Windows XP or Windows Vista. If you purchased your computer from a big retailer such as Dell or HP you should have a restore disk, if not call customer support and request one.
• Take an inventory of your hardware and software. Download all the latest drivers for your hardware (which can be found on the respective hardware manufacture’s website.) Be sure that you especially get your network driver beforehand because the most common problem that I run into is a new install without the network card installed. Also make a list of your software and download the latest versions. Burn all of this to a CD.
• The reformat process is not that complicated but do a Google search if you are not sure.
• After the operating system is installed, install your drivers from the burned CD.
• Update Windows. Do this before going ANYWHERE on the Internet.
• Install a good antivirus. I recommend Avast! (http://www.avast.com/)
• Reinstall all of your software from the Internet and burned CD.
In the end this may end up costing you money if you don’t have the Windows install disk or you take it to a repair shop and have them reformat the computer. Please don’t underestimate the importance of this and not reformat because the attacker not only has access to your Yahoo! Messenger but also your entire computer. He can see what you are doing, see what you are typing, and see everything else you do on the computer. It sounds like he is just giving you a hard time by harassing you and your girlfriend but don’t give the jerk anything else to play with such as your email or in the worse case, online banking information, PayPal or credit card information. If this were me, I would have the entire machine reformatted as quick as I could turn it off.
DO NOT DELAY! This is a critical security problem and needs to be address immediately!
P.S. For full completeness an attack like this can be waged if the attacker is on the same non-switched network segment. Just like any network communication, all traffic on a single segment can be sniffed and possibly altered. This is increasing rare because most networks are now run through switches (http://en.wikipedia..../Network_switch) and not hubs (http://en.wikipedia....iki/Network_hub). Switches isolate each individual segment so there is only one computer on that segment and sniffing cannot be performed. This would require a man in the middle attack (http://en.wikipedia....e-middle_attack) so it would still take some work to get this scenario to work. For the original question, you should ignore this because your chances for this happening are around .0000001%.