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Since the past few days, I noticed that my router was a bit slow, and was restarting by itself at times. When looked at it's logs, they had entries like:

Friday Jul 13 13:09:02 2012 1 Blocked by DoS protection 59.145.XX.XX

I thought I was being bombarded by packets from the specified IP, and contacted the owners, only to get told that the router was instead preventing a machine from within my network from spamming the said IP.

Eventually, I narrowed the bad traffic down to my MBP. i.e. I'd occasionally get those entries in my router when my MBP was connected, but not for any of the other machines. To find out what was causing the issue, I installed Private Eye, but that didn't flag anything.

Finally I ran Wireshark, and saw that something was constantly sending out a lot of packets to seemingly random IPs. There was a bit of a pattern in the order of packets though.

  1. My machine would send an ICMP packet to a remote IP.
  2. That IP would then get back to my machine with a TCP SYN, attempting to connect to 30149 (could've been randomly chosen, but this port no. didn't change for over 5 hours that I was monitoring it).
  3. My machine would respond back with an [RST, ACK], probably since there was nothing listening at that port, thus terminating the connection.
  4. There was also a UDP packet to the same port (30149) in between.
  5. I remember seeing a BitTorrent connection (as identified by Wireshark) in addition to all these for some IP, but that was a one-off instance (a single packet, maybe), and I couldn't quite make sense of the data.

I've seen a few other posts where people have complained about strange traffic, and the answer usually is that it's just some idle traffic from the machine. But this definitely doesn't look like idle traffic. This sequence of packets is being sent constantly. Actually, these steps keep happening in parallel for multiple IPs (but their relative order seems to be preserved). So, there's quite a bit of traffic. When I look at the Activity Monitor, the traffic seems to be a steady 5-6 KB/s, which isn't a lot, except that it's spam.

I'm trying to narrow all this down to a single process (or a set of them), which'd hopefully help me make better sense of the situation. I haven't been successful so far though.

'lsof -i :30149' didn't help, since there's nothing listening there.

I've installed Little Snitch, but haven't got around to trying it (waiting for a virus scan to complete to restart the machine and finish it's installation). I'm not quite hopeful of it identifying the culprit though, considering Private Eye didn't identify anything.

So, does anyone have any suggestions as to how I can figure out the process that's generating this traffic? Has anyone seen similar traffic? Any help is appreciated.

-- EDIT --

Ran Little Snitch, but that didn't turn up anything. i.e. When I run Wireshark, there's still the same strange traffic. But Little Snitch doesn't prompt me about those connections, possibly because no connections are established. So, I still have no clue as to which process is generating this traffic.

-- UPDATE --

I had the steps wrong. The sequence starts with an external IP trying to send a packet to my TCP/UDP port 30149, which is refused by my machine. In case of TCP, it turns out to be an [RST, ACK]. And in case of UDP, it seems to send back an ICMP error message (never knew an ICMP message would be sent back in response to an UDP error). Here's a screencap of the Wireshark capture, filtered to one of the IPs: Wireshark Capture - Filtered to one IP

Here's another screencap, showing typical network activity: Wireshark Capture - Typical Network Activity

192.168.2.5 is the MBP.

So, me trying to narrow it down to a local process was the wrong idea, since all these are inbound connections.

Strangely, I see this traffic only on my broadband connection. When I capture while connected through my datacard (with wifi turned off, which's usually connected to the broadband connection), none of this traffic is seen. So, it looks like all these IPs are trying to hit my public IP (broadband), which gets assigned to me dynamically (but it still stays the same for over a month). Maybe the previous owner of the IP was infected, and this is just a result of that. Not sure. I still don't understand why this traffic shows up only on the MBP. It didn't show up when I set up a capture on other (Windows) machines.

At this point, I'm utterly confused, and I'm sorry if all this looks a bit nonsensical. I know I should rephrase/rewrite the question. I'll get to that later.

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1  
It does sound like a malware attempting to connect to a C&C server. I'm not sure though. –  Terry Chia Jul 14 '12 at 2:30
    
I think I'd agree with Terry - the symptoms seem to be in that area. My take would be to (if possible) wipe and rebuild, because if there is hidden malware on that system it could be doing anything. –  Rory Alsop Jul 14 '12 at 9:23
    
I was hoping to identify the malware that's causing the issue before having to reinstall. But yeah, if I don't get something soon, I'll just wipe my HD and start afresh.. –  CodeMangler Jul 14 '12 at 16:56
    
It is pretty hard to detect malware without having a clean system state to compare it against. There is just too many places a malware can stay hidden in an operating system. –  Terry Chia Jul 14 '12 at 17:01
    
The issue turned out to be that somebody/some app configured my router to forward <my_public_ip>:30149 to 192.168.2.5:30149. Not sure when that happened or why, but that caused all that traffic to show up at the MBP. Now that I've removed the entry, that traffic no longer apppears. I'm just glad to confirm that my MBP isn't infected. :) –  CodeMangler Jul 16 '12 at 13:10

2 Answers 2

up vote 6 down vote accepted

I'd normally suggest netstat -n -p in linux, but the Mac/BSD version doesn't associate with connections with processes unlike the linux version.

So maybe try to see if sudo lsof -lnP +M -i4? sudo in case its not your user id thats running it, -lnP to not convert UIDs/ip addresses/ports to usernames/domain names/common services, +M for portmapper registration info, and -i4 to see all ipv4 open connections.

Maybe write a watch script to grep for that port. Granted again macs don't have a watch command but you can simulate with a quick script like:

sudo su
while true; do lsof -lnP +M -i4 | grep '30149'; sleep 1; done

and eventually quit by Ctrl-C.


Looking at your edit; I think your computer may be fine, but you probably should reconfigure your firewalls/port forwarding rules on your router.

You should have your router act as a firewall and drop/ignore random packets that do not originate from a connection you initiated (and are not sent to a port for a server you are running that should be accessible by the outside world). Let's say your ISP issued IP address is 100.101.102.103 and my computer is 1.2.3.4 and your macbook pro is one computer behind your router with a local IP address 192.168.2.5. If I send a packet from my machine to that 100.101.102.103 on port 30149, your router should have no reason to forward that packet to 192.168.2.5 (versus any other computer connected to that router). The router should just drop it.

This is contrasted with a legitimate request that your computer initiated. E.g., if your router knows that 192.168.2.5 has requested a connection with 1.2.3.4 at some port (say port 80 at my end for a webserver I host; some random port at your end say 58325) then your router will direct received packets from 1.2.3.4 directed to 100.101.102.103 at port 58325 to your macbook at 192.168.2.5 port 58325 knowing that's who the packet is for (your router remembering the IP + port combo originated your computer) so by default will forward it appropriately.

This is also contrasted by say if you want to host a server of some sort on your computers behind your router. Then you need to define some port forwarding rules for outside computers that initiate a connection to 100.101.102.103 at some port to then get mapped to the correct port on the correct computer. E.g., if you have a macbook pro and a linux box (192.168.2.3), you may have connections to 100.101.102.103 on port 22 go to the linux box ssh port (192.168.2.3 port 22), but maybe have 100.101.102.103 on port 23 get forwarded to the macbook pro's ssh port (192.168.2.5 port 22).

In summary: your router should not have any port forwarding rules set up, unless you are running services like http/ssh/nfs/cifs, etc at known ports that need to be accessible to the outside world.

share|improve this answer
    
Thanks for the suggestion. :) I'll try that out tonight. –  CodeMangler Jul 14 '12 at 16:57
    
So, it looks like there may not be a process that's causing this traffic after all. Haven't quite confirmed that yet, but most of the traffic looks inbound. Thanks for the script though. :) –  CodeMangler Jul 14 '12 at 19:27
    
@CodeMangler - I saw your edit; and have a new response above. –  dr jimbob Jul 16 '12 at 7:06
    
Thanks :) I found port forwarding rules on my router, configured to forward <my_public_ip>:30149 to 192.168.2.5:30149. My MacBook happened to stick to 192.168.2.5 for the past few days, which's why I was seeing all that traffic only at the MBP. Anyway, I've reset my router configuration and disabled UPnP, just to be safe. Thanks for the solution. :) –  CodeMangler Jul 16 '12 at 13:00

Your computer is fine imho.

I think you're being scanned and it's a targetted scan on port 30149. I don't know of any vulnerable service running on that port but in my mind someone was looking for something on that port. I suspect they were scanning a large netblock and your public, IPv4 IP from your ISP was just one of many scanned.

I don't believe it's malware C&C traffic as everything is initiated inbound as far as I can see.

The attacker is performing the scan on port TCP and UDP port 30149 and as per their respective RFCs, your MBP is responding correctly when a destination port is closed (RFC 793 and 768 respectively) - RST/ACK to the TCP Syn attempt as the port on the MBP is closed and similarly for UDP with an ICMP Port Unreachable (type 3, code 3) so that's all good.

If you perform a reverse-dns lookup dig -t x IP on the various IPs that are attempting to connect to you, you'll see that they're quite geographically diverse. Given the short time-frame of the attack, this leads me to believe that the person attacking you has a small botnet and obviously, if they're decent, you shouldn't be able to see their real IP.

  • 121.54.54.36 - no reverse record but whois shows => Wireless Broadband, Makati City, Philippines

  • 86.176.100.134 - host86-176-100-134.range86-176.btcentralplus.com => ISP in UK

  • 49.156.159.35 - no reverse record but 'whois' says => CityOnline Services Ltd, Bangalore

  • 78-60-80-5 - 78-60-80-5.static.zebra.lt => Media Company in Lithuania

  • 81.203.200.189 - 81.203.200.189.dyn.user.ono.com

  • 46.240.50.22 - no reverse record but part of RIPE so in Europe

  • 78.165.164.69 - 78.165.164.69.dynamic.ttnet.com.tr => some kinda ISP in Turkey

  • 186-228-40-136 - 186-228-40-136.ded.intelignet.com.br => Brazilian Postal Service or something

  • 81.203.200.189 - 81.203.200.189.dyn.user.ono.com

  • 90.14.19.81 - ALyon-152-1-212-81.w90-14.abo.wanadoo.fr

  • 41.96.92.136 - It's in Algeria but no reverse DNS

These IP addresses are all from systems (most likely on broadband connections) that have been compromised and similar to you, they have a static IP from the ISP (the hostname is a giveaway in most cases above).

So it's pretty standard inbound scanning that you see everywhere on the Internet. 'dr jimbob' has made some good suggestions and you should tighten up the rules on you external router to essentially only outbound initiated traffic (this might will 'active ftp' but hopefully you're neither using ftp and if you are, it's 'passive'). You can create some ACLs so that you don't leak information suck as ICMP Type 3 messages when ports/services are closed. I could go on forever here but there's loads of papers here on how to create perimeter protection (ignoring the fact that there's no real perimeter these days).

Finally and very interestingly, if you look here at Dshield, you'll see there was a spike worldwide in scanning port 30149 on June 29th/30th.

Most home routers (well the decent ones) have iptables on them and there's loads you can do on that - see the HowTo.

share|improve this answer
    
Yep, the traffic to my MBP stopped once I removed the port forwarding rules. My router's just a basic home router, and doesn't really give me a lot of fine grained control, so no ACLs. Anyway, so far, nothing inside the network's registering any strange traffic, so that's good. Thanks for the analysis and all the info. Also, thanks for the Dshield link. Didn't know about it, and it has a lot of useful stuff. –  CodeMangler Jul 16 '12 at 21:19

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