Very peculiar Telnet probing (possibly spoofed?)

Thu Sep 9 05:48:40 UTC 2004

I have been rather reluctant to post this as I had hoped it was just a 
fluke.  But this has been going on for nearly two weeks.  We are getting 
banged by telnet probes from SE Asian sites... over 1000 different ones 
in all attacking the same address range.  I suspect but cannot prove 
that the packets are being spoofed as we are dropping (not resetting) 
the probes, yet they continue.  There are repeated probes from the same 
IP address for about 15-20 minutes or more, then it moves along, but the 
resulting router logs blocking them looks initially random (from SE Asia 
sites).  Is someone out there to make a bad statement for APNIC by 
spoofing the origins, or is this some co-ordinated attack/probe.

The high-order octed of the attackers is consistently within one of 
these /8 netblocks (though not evenly spread, and cluster around certain 
address blocks as shown).  I haven't heard of anything like this (other 
than recent SSH brute force, but this is telnet).

I'm getting attacks from:

159.226.x.x
202.x.x.x
203.x.x.x
210.x.x.x
211.x.x.x
218.x.x.x
219.x.x.x
220.x.x.x
221.x.x.x
222.x.x.x
61.x.x.x

Again, thousands of probes, about 10-20/sec when they're on a roll.  
These are attacks on a /18 subnet with only a small subnet (our secured 
servers) that is in danger (we block/drop telnet inbound to dynamic NAT 
but accept for static server translations)..

It is almost as if someone were spoofing the asian addresses to 
'simulate' an Asian attack, but what with the big bot-nets, I suppose 
that's a possibility too, but all these addresses (that I looked at) 
were SE Asian in origin.

After passing the 1000 scanner benchmarkk today, with some manual 
aggregation of obvious problem areas, it still continues.

Anyone else seeing this?  We're getting this more often than the SSHD scans.

Jeff Kell
Systems/Network Security