Google & "UDP flood" action


So to get straight to the point, I'm running Sophos UTM (FW Ver.: 9.203-3, Virtual) Home License and, as the thread title shows, browser-based Google products are affected by the IPS and some of its traffic are being tagged by the IPS as "UDP flood" firewall rule 60013, which is to Drop UDP_FLOOD attempts

As a result, some Google products will be capped at 2mbps download speeds. Strangely enough, it only happens to one wired client and not any virtualised clients nor wireless clients (so this means neither the LG Smart TV running YouTube nor the Android smartphone running Google Maps experience this issue.) When this plays out:

  • YouTube will load videos at 2mbps, causing buffer to 1080p videos and less often to 720p videos; and
  • Google Maps will load its chunks of map and image data slowly

Now, I can definitely turn off UDP flood protection, but that leaves a gigantic gap on my network. It's probably not the best practice when the UTM is responsible as the gateway between the Internet and my network at home. You now understand why this is probably something I would consider to avoid. I had disabled it for a minute and it definitely increased the loading speeds to what my ISP provides, which is 30x more than what it was throttling me to. As of right now, it's enabled.

Has anyone else experienced this issue? Has anyone found a fix for this? This started happening probably around the time where the OpenSSL Heartbleed vulnerability was discovered, if not a month or two before it.

UPDATE: Alright, so here's what's getting hit by IPS so that we all have that general idea...

IP of Google is the source IP. 
WAN IP is the destination.
Action is UDP Flood
Source Port: 443
Destination Port: Some random port on the 50000~60000s. 

Last time I checked, 443 isn't exactly UDP for the nature of what's being transported and a corporation like Google would keep atop for any such UDP floods to prevent it from happening.

Second Update
Please don't tell me this is too difficult. It has to be some simple explanation.
2014:07:14-16:40:20 core ulogd[4786]: id="2105" severity="info" sys="SecureNet" sub="ips" name="UDP flood detected" action="UDP flood" fwrule="60013" initf="eth1" srcmac="[Source MAC]" dstmac="[Destination MAC]" srcip="" dstip="[My WAN IP]" proto="17" length="1228" tos="0x00" prec="0x00" ttl="57" srcport="443" dstport="55971"

  • Why not just make an Exception?  Probably like 'traffic coming from' and 'using service {TCP&UDP : 443->50000:60000}'.  Any luck with that?

    Cheers - Bob
  • In reply to BAlfson:

    Why not just make an Exception?  Probably like 'traffic coming from' and 'using service {TCP&UDP : 443->50000:60000}'.  Any luck with that?

    Cheers - Bob

    It would work if Google stuck with one IP the entire time I'm using their products. Since it's almost a different IP every time, the workaround won't really last long. I'd have to go edit the Intrusion Prevention exceptions every time I notice a drop to 2mbps.

    Would you have any idea why this happens to primarily one client as opposed to every client on the network?

    Huge Update:

    Alright! So I nailed it down to really being only one PC. However, Sophos still has something to do with this because the IPS catching this is still a part of the issue. 

    According to Wireshark on two different computers, one of them treats the HTTPS packets as TCP all the way. The one I'm using that's affected treats the handshakes/Client Hello/Certificate/all that as TCP but the rest of the packets following during the connection are UDP. 

    What!? (My head hurts even more now.)

    So what setting could be messing with this? Something I can change on Sophos or something on my Windows Laptop?

    Problem solved. The reason why - There was apparently an update that's part of SPDY, something, I believe, Google is developing with an end result called "QUIC", an experimental HTTPS-over-UDP system that uses a heavily unusual amount of UDP packets.

    It has been integrated as part of Google Chrome (and Opera.)

    My last say on this is: I think those who contribute to the development of Sophos should take a close research at QUIC. This could become a bigger problem in the future, if not already by now.
  • Hi, for now you may have to disable UDP flood protection.

  • Has there been any update for this?  I recently installed splunk and am seeing luckily for me this was my first google result to describe why google is sending my https udp packets!!  Is there a way to set up an exception to allow this traffic?
  • In reply to polyphemus11:

    Has there been any update for this?  I recently installed splunk and am seeing luckily for me this was my first google result to describe why google is sending my https udp packets!!  Is there a way to set up an exception to allow this traffic?

    Hi, for now you may have to disable UDP flood protection.

  • i've tried this with my firewalls and have not hit this issue....have you updated to the latest versions and tried again?
  • In reply to BarryG:


    I have noticed this the past few months and it's been driving me crazy, but I have found a workaround as in nearly a year this hasn't been addressed by anyone else as far as I can tell.

    I created a new network definition, called it HTTPS (UDP) for want of anything better, type:UDP, Source:1:65535, Destination:443, then added this as an exception for UDP Flooding detection. I thought this was at least better than completely disabling detection.

    I also have an exception for outbound from my internal network that also disables all flooding detection, as this was causing issues with a few games I was playing. Perhaps I may revisit this setting at another time.

    For now, Google's YouTube and YouTube Gaming streams work without a hitch at full 1080p60
  • In reply to Taomyn:

    Great research from previous posters, thanks for creating a reference for this issue.

    I took a slightly difference approach as opening up all UDP from any source and port going to 443 and disabling all flood detection was not acceptable here.

    I noticed all of these IPS blocks were coming from the 74.125.x.x range and host lookups verified that these were all hosts from Google.

    A quick ARIN search validates that Google has been allocated the entire 74.125 class B network.

    Therefore, I created an IPS exception that disables the IPS/Portscan and TCP/UDP/ICMP flood detection for the 74.125 range only.

    (edited to include more detailed screenshot)

  • In reply to BrentCrawford:

    Hi, we are having the same issue here. 
    Before disabling UDP flood detection: couldn't this be fixed somehow different?

    [code]2016:09:26-11:15:33 vpn ulogd[5341]: id="2105" severity="info" sys="SecureNet" sub="ips" name="UDP flood detected" action="UDP flood" fwrule="60013" initf="ppp0" srcip="" dstip="OUR-WAN" proto="17" length="1378" tos="0x00" prec="0x00" ttl="56" srcport="443" dstport="39729"[/code]

  • In reply to DavidSchmidt:

    Thanks for posting that, David!

    For my clients, I configure the same subnet as Brent ( with a Service of UDP443:1-65535, but I only except UDP Flood protection, not the other capabilities.  It looks like I'll need to add to that Exception.

    Cheers - Bob

  • In reply to BAlfson:

    Hi Bob, thanks for the answer :)

    I actually went through the IPS logs and identified (via NSLOOKUP) the IP ranges of Google and some other big companies I would expect to not be sending UDP flood.

    After adding those as exceptions (just UDP flood detection) my daily log of IPS shrinked from ~20-30MB to ~1-2MB 

  • Hi All,

    Just to update, Google introduced QUIC protocol that communicates on UDP port 443. The protocol comes into picture while using Google Chrome as the web browser; incognito browsing on chrome will not use QUIC. The suggestion by Bob and Brent has to be considered when AntiDoS is configured.


  • In reply to sachingurung:

    It appears Google has a huge number of IPs addresses that resolve to subdomains on Is there an easy way to tell UTM9 that any subdomain on is okay to allow through the firewall? 

  • In reply to Dlabun:

    No.  Note that this is only an issue in organizations that allow the use of Google Chrome.

    Cheers - Bob

  • In reply to sachingurung:

    Hi everyone,

    today I stumbled about this thread, cause I've viewed our IPS logs, as we got a new SG310 I turned on IPS.

    I recognized the suggested answer here, but had no luck. As there are a lot of these Google networks. So I decided to simply allow all of the QUIC traffic by creating an exception by service.

    But, this does not work - and I don't know why.
    I still get blocked entries like this:
    2016:11:03-19:21:21 gate-1 ulogd[5385]: id="2105" severity="info" sys="SecureNet" sub="ips" name="UDP flood detected" action="UDP flood" fwrule="60013" initf="eth2" srcmac="00:xx:xx:xx:xx:xx" dstmac="00:xx:xx:xx:xx:xx" srcip="" dstip="xx.xx.xx.xx" proto="17" length="113" tos="0x00" prec="0x00" ttl="60" srcport="443" dstport="62099"
    Has anyone an idea why the rule is not working?