We recently got an abuse report of an IP address in our net range. However, that IP address isn't in use in our networks and the covering network is null routed, so no return traffic is possible. We have external BGP monitoring, so unless something very tricky is going on, we don't have

Nmap has an option to "hide" your real IP among either a provides or IP list of IP addresses. " D *<**decoy1**>*[,*<**decoy2**>*][,ME][,...] (Cloak a scan with decoys) Causes a decoy scan to be performed, which makes it appear to the remote host that the host(s) you specify as decoys are scanning the target network too. Thus their IDS might report 5–10 port scans from unique IP addresses, but they won't know which IP was scanning them and which were innocent decoys. While this can be defeated through router path tracing, response-dropping, and other active mechanisms, it is generally an effective technique for hiding your IP address." http://nmap.org/book/man-bypass-firewalls-ids.html On 11 Mar 2015 02:17, "Steve Atkins" <steve@blighty.com> wrote: On Mar 10, 2015, at 4:40 PM, Matthew Huff <mhuff@ox.com> wrote: part of our prefix hijacked.

I assume the source address was spoofed, but this leads to my question.

Since the person that submitted the report didn't mention a high packet rate (it was on ssh port 22), it doesn't look like some sort of SYN attack, but any OS fingerprinting or doorknob twisting wouldn't be useful from the attacker if the traffic doesn't return to them, so what gives?

BTW, we are in the ARIN region, the report came out of the RIPE region.

Either the reporter doesn't know what they're talking about (common enough) or someone is scanning for open ssh ports, hiding their real IP address by burying it in a host of faked source addresses. That's a standard option on some of the stealthier port scanners, IIRC. Cheers, Steve