What's up with Yahoo messenger?

[Jeff Kell <jeff-kell () UTC EDU>]

Today I noticed an unusual number of "possible spambot" and "telnet scanning" alerts over the weekend.  In tracking 
these down, I found almost all of the destinations were Yahoo!  Mostly 216.155.193.x and 66.163.172.x hosts.

In checking the packet payloads, it was Yahoo messenger.

On ports 20, 23, and 25?  Gee, this blows my security model astray.

Apparently this has been going on for some time.  I found this little reference at 
http://www.wackyb.co.nz/menu/Yahoo_Messenger_v6_Connection_Issues/ :

> Basic Connection:
> Protocol:               TCP or HTTP
> Servers:                scs.msg.yahoo.com
>                         scsa.msg.yahoo.com
>                         scsb.msg.yahoo.com
>                         scsc.msg.yahoo.com
> Port:           20, 23, 25, 80, 119, 5050
>                         (also 8001, 8002)

Does this surprise anyone else as it did me?

Do you make provisions to allow for Yahoo IM even though you might block some of those ports?

Jeff