is it possible to see others yahoo messenger ?

ya I found some decoder softwares which can do that work ...

may be they are using such softwares ...

but I want to know is there any way to know the IP Address  of a person with his yahoo messenger ID ? if I know when he is online ...

thank you in advance ...

Yahoo Messenger privacy settings
http://privacy.yahoo.com/privacy/us/mesg/details.html
You have certain choices about whether to add friends, be added as a friend, or ignore other members. Adding someone to your ignore list will also ignore PC-to-PC calls and related voice messages from that person.
Yahoo! does not save your instant messages, but we do make some functionality, such as archiving and the ability to print and save messages, available to members so that they may retain records of their instant messaging communications

By default, Yahoo! Messenger will archive your message history for the current session, until you sign out. When that that session ends, the message archive will be deleted.
To change your archiving preferences in Messenger, choose Messenger > Preferences > Archive
Please be aware that even if you choose not to save your message history, members you correspond with may opt to use the functionality available in their version of Messenger to save the communications.

Sorry missed your second comment, if this person canchat to you he must be in your list otherwise look the from message it shoudl contain his nickname.
There is a couple of small freebies that can list the ip addresses of anyone accessing yoru computer
My personal favourtie is Active Ports and I think this will do the trick for you.
Whenever any incoming accesses your computer it regesters it in red and you can lookup who is and ip address.
screen shot
http://www.snapfiles.com/screenshots/activeports.htm
http://www.majorgeeks.com/Active_Ports_d682.html

Port Listener XP
http://www.snapfiles.com/get/portxp.html

Is it possible to trace a person chatting to you simply put NO!
If the person is not on your contact list all messages come thru a server.
All you can do is my above suggestions or  use stealth or block them when they do appear.

Here is my comment of what i think about this question...
First off there is no such little program available to do that,
my recomendation for you, is to scam you computer with a
good anti trojan, keylogger, virus, hoax, spyware, and more.

thats the only way someone can see what are you doing in YIM
the other thing that Merete is saying, is true, i agree with that.

and about trace someone in Yahoo! using the old netstat, i don't
think that will help you to understand what is going with you buddy.

thats just to get the other person ip, then what you can do with that?
Nothing but know the conutry, ISP, and few more things from the user.

Now on the other hand, if what you are looking for is a Hacking tool,
thats another story, and i don't think someone is willing to help you with that.

< I heard that there is a software to view others messenger ...

No way, if this wwere true no one would have an account at yahoo.

< since some days someone is seeing my messenger chats with my friends ...  I have changed my password still he could see what I am chatting with my friends ... and sending those messages to me ...

It looks that you have been hacked with a trojan or kind of utility.

< does any one know such software and how to bypass this software ?

You can easily run a tasklist command on your windows console and post the results to someone to help you.

Or you can use http://www.merijn.org/programs.php#hijackthis

Also use an antivirus(bitdefender can do the job) and scan your computer for malicious software.

Thank you Merete ... ya it was usefull tool to see the IP addresses of persons accessing my system ...

but as Zak-R said what can I do with IP address... I don't want to go behind all persons accessing my computer but I want to bypass those attacks ...

I mean I want to secure my messenger from them ...

ch2
>>No way, if this wwere true no one would have an account at yahoo.

yes ch2 there are some softwares which can secretly switch the archive on and access the messages with out knowing the password....   they are available for MSN and yahoo ..

for example ...
http://www.topshareware.com/MSN-Yahoo-Message-Archive-Decoder-Viewer-download-39282.htm 

http://www.softpedia.com/get/Internet/Chat/Instant-Messaging/Super-Yahoo-Messenger-Archive-Decoder.shtml 

but I am not sure if these softwares help to see messages of others from a different computer ...

Those software are used to view local logs like notepad to read text file.

With this utility i can't get into your yahoo mail.

A malicious user can use a trojan to donwload those log files from your computer and then use the software below to read them, nothing else.

View yahoo and MSN chat logs of yourself, your spouse, your kids, or anyone, without logging in to Yahoo or MSN. Either you want to read your own chat logs or you want to spy on your love one, this program allows you to view all the chat conversation without knowing the password. You can also turn on someone’s archiving option and secretly log his or her conversation.

http://www.topshareware.com/MSN-Yahoo-Message-Archive-Decoder-Viewer-download-39282.htm

Hey raysee...
the link of the program you posted, thats just for you to see the log of everyone
that had use you Yahoo! Messenger in your computer nothing else.

Now if you want to avoid this, or if you are afraid you mom or anyone can see this
after you done chating, just go to: C:\Program Files\Yahoo!\Messenger\Profiles
and delete the folder that have the nick name you was chatting with and thats it.

In the case of Yahoo! Messenger there is no defense against vulnerabilities,
there is no shield to protect your self from any explotation of extraction hoax.

If you want to stay clean while you chat with Yahoo! Messenger, do not acept any
picture or file from anyone, or don't try to acept invitation from user you don't know.

Also, try not to donwload programs that promise to give you option for this for that, etc.
those programs are full with many tricks to hack you pc and you Yahoo! accout + u mail.

Take it easy with Yahoo!, but yeah, is better Yahoo! than any other messenger...
Like => MSN, PalTalk, AOL, ICQ, and many other unknown messenger :-)

Thank you so much friends ...

ya Merete your mail was really helpful ..

I hope if I install those softwares and clean my system then may be it could be better to prevent attacks ...

thank you and you are welcome, hope you have no more problems with your privacy.
Be well and happy
regards merete

Sorry Merete ...