How to block this type attack?

Guest · Feb 3, 2015, 12:14 AM

My LAN Server send many outgoing TCP packets and states exhaust

I use tcpdump

20:53:49.280616 IP a.b.c.d.34574 > 122.226.161.51.7000: Flags S, seq 1758704997, win 61437, length 0
20:53:49.280635 IP a.b.c.d.49465 > 122.226.161.52.7000: Flags S, seq 1985270926, win 64414, length 0
20:53:49.280657 IP a.b.c.d.31893 > 122.226.161.53.7000: Flags S, seq 1917753334, win 63902, length 0
20:53:49.280677 IP a.b.c.d.34245 > 122.226.161.54.7000: Flags S, seq 1672920662, win 63726, length 0
20:53:49.280698 IP a.b.c.d.43872 > 122.226.161.55.7000: Flags S, seq 1962787171, win 64507, length 0
20:53:49.280716 IP a.b.c.d.54136 > 122.226.161.56.7000: Flags S, seq 932930625, win 60665, length 0
20:53:49.280734 IP a.b.c.d.2144 > 122.226.161.57.7000: Flags S, seq 1030524293, win 61229, length 0
20:53:49.280753 IP a.b.c.d.50707 > 122.226.161.193.7000: Flags S, seq 346594498, win 60130, length 0
20:53:49.280771 IP a.b.c.d.29773 > 122.226.161.194.7000: Flags S, seq 612510536, win 61080, length 0
20:53:49.280789 IP a.b.c.d.35494 > 122.226.161.195.7000: Flags S, seq 877077015, win 63727, length 0

Then I add tcp rules and use "Maximum new connections / per second(s) (TCP only)" option (10/1)

But virusprot table is empty

Anyone know how to get it working?

Thanks

Derelict · Feb 3, 2015, 12:26 AM

Why is your LAN server port scanning?

Guest · Feb 3, 2015, 12:46 AM

To put it precisely，ths server is hacked and it attack others

But I don't know why it not working when I use the virusprot settings

Derelict · Feb 3, 2015, 12:49 AM

So fix the damn server.

At least put a block rule on LAN that blocks from that server port any to any port tcp/7000 until you figure it out.

Don't hassle with some package that obviously doesn't work very well. Shut that nonsense down.

cmb · Feb 3, 2015, 1:20 AM

@Derelict:

So fix the damn server.

At least put a block rule on LAN that blocks from that server port any to any port tcp/7000 until you figure it out.

Don't hassle with some package that obviously doesn't work very well. Shut that nonsense down.

This. Though take it a step further, block everything sourced from that server until you figure it out and get it cleaned. Ideally take the infected server off the network entirely, you don't want a compromised server online.

johnpoz · Feb 3, 2015, 11:43 AM

Unplug the damn thing!! WTF people???

Guest · Feb 3, 2015, 3:09 PM

Sorry, My English is bad….

I think everyone misunderstand this thing

When attack occurs,states exhaustion, i unplug WAN port,and test Internal

I hope attack can be blocked by pfsense first time,and prevent states exhaust next time

SO Simply I wanna to know how to avoid hacked server(not managed by me) exhaust states

Instead of use pfsense firewall（i manage it）and hacked server is still online

Express bad was my fault....

lowprofile · Feb 3, 2015, 3:18 PM

Yeah….

Anything can happen when they are inside your network. How much memory do you have?

Harvy66 · Feb 3, 2015, 3:22 PM

He wants to know how to reduce the chance of a single hacked box from inadvertently taking down the entire network from state exhaustion.

PFSense does have an option in the top left web admin menu that allows for a reduction of state lifetime as states fill up. Simply put, the more states you have, the shorter they live without being kept alive. Since the issue is SYN packets creating states, but no real traffic after the fact, you don't want these states lasting the default 24 hours. As states fill up, the idle life will approach 0 seconds, allowing these unused states do quickly die off.

Derelict · Feb 3, 2015, 4:27 PM

@johnpoz:

Unplug the damn thing!! WTF people???

My concern is not with OP, but with everyone else. He obviously doesn't care he has an infected computer on his network and wants to do research with it.

kejianshi · Feb 3, 2015, 4:40 PM

If you have a hacked box in your network, do not try to clean it or fix it.

Wipe it. Reinstall from fresh. (Not from a pirated ISO that contains lord know what)

Reconfigure.

Done.

In my opinion, there is no such thing as good virus protection. Some just suck slightly less than others.

If you have an OS that needs virus protection, no matter what virus protection you buy, its only a matter of time till its infected.

Get used to wiping and reinstalling if you use windows in a way that exposes it to risks.

doktornotor · Feb 3, 2015, 5:12 PM

Help: I Got Hacked. Now What Do I Do?

The only way to clean a compromised system is to flatten and rebuild. That’s right. If you have a system that has been completely compromised, the only thing you can do is to flatten the system (reformat the system disk) and rebuild it from scratch (reinstall Windows and your applications). Alternatively, you could of course work on your resume instead, but I don’t want to see you doing that.

P.S. Let me repeat: Unplug the infected shit from Internet!!!

kejianshi · Feb 3, 2015, 5:21 PM

BTW - I would guess whoever is in your network is scanning for new things to infect, CC or private info to steal…

All I know for sure is it isn't good so unless you are a forensics expert working for law enforcement, can't imagine why you would just let the hack keep running.