I spent one morning looking at Yahoo's mail security ...here's what I've found and how I did it.....

I created an account whilst dialed into Pipex. I logged out and closed my browser. On reopening the browser I pasted in the following URL:

ht tp://mail.yahoo.com/py/ymTop.py?y=1

and this took me back to my account with out any error messages or prompts for a login. I then closed my browser, disconnected from Pipex and dialed 
into Globalnet. When connected I opened my browser and pasted th e same URL:
And was taken back to my mail-box! This made me think there must be a cookie controlling this...sure enough there it was. (1 of 3)

One, the user@mail.yahoo.com cookie in the rough looks like this :


YM.Login
id%3dreIvr96lzVC4g%26s id%3dtMZu7cDVk5V9e%250a%26ts%3dX%2588B%2540
%25f5%2517%25cd%2599%25dc%253f%259c%25c1Y
mail.yahoo.com/
0
4227368448

29309637
2474945552
29188238
*
YM.Pref
farm%3d1%26silo%3dms4%26
email%3dmail-name%40yahoo.com%26head%3dbrief %26fwd%3dattach%26fontsz
%3dnormal%26msgwidth%3d72%26order%3ddown%26inc%3d50%26goto
%3dmsgmail.yahoo.com/
0422736844829309637247514555229188238* 
but with all the Hex stripped out it slightly more managable:

[YM.Login]
id=reIvr96lzVC4g &< br>sid=tMZu7cDVk5V9e%0a &
ts=X%88B%40%f5%17%cd%99%dc%3f%9c%c1Y
mail.yahoo.com/0422736844829309637247494555229188238*


[YM.Pref]
farm=1 & silo=ms4 & email=mail-name@yahoo.com & 
head=brief & fwd=attach & fontsz=normal & 
msgwidth=72 & o rder=down & inc=50 & goto=msg
mail.yahoo.com/
0
4227368448
29309637
2475145552
29188238
*


After being logged off for around an hour I reconnected to the Internet and pasted that URL again and got back in......this made me suspic ious. I clicked on exit and checked the whole "exit" document. Down the bottom I found a link :

Log off completely.


Nice of them to warn you and put it way down the bottom. Most new users will not realise that the log off process is a double actio n...if you log off "completely" then the cookie is removed from the Temporay Internet Files directory.

What does all this mean ?
Security wise if you can get physical access to a machine that someone has used to collect their mail and not done the d ouble log off then you can 
access their account perhaps ad infinitum. (I don't know yet if the cookie has a TTL so to speak.) In practice this means you'll be cracking a friend's,
work (or school) colleague's or family member's account. Good for s nooping on your girlfriend's e-mail activities too.... . Unfortunately
you can't copy it to a floppy disk and save it in your own computer's Temporary Internet Files directory because of the ":" ...What you'd need to do is copy it to a flo ppy anyway...so you've got what info you need...then, now here's the complicated part :

Set your own PC up as a webserver as well as a DNS server (if you've got NT Server your laughing). Create a DNS entry for mail.yahoo.com and use the loopback (127.0. 0.1). Then create an htm file with the necessary script to impart a cookie with this same 
information. Connect to mail.yahoo.com (you'll actually loopback) and the cookie will be downloaded to the Temp Net files Directory....

A big hassle to do...pr obably easier to watch them type their password ;o) but it's knowing how it can be done..that's the important thing. Btw, just for any of you jokers out there...I've modified the security identifier and the e-mail account name etc....I'm not gonna give yo u a copy of my real cookie then tell you how to exploit it...get real ;o) There'll be other ways to crack yahoo, of course....this is just my offering on the matter...for now anyway.