Increase in Protocol 47 denys

Published: 2016-12-29
Last Updated: 2016-12-29 19:39:08 UTC
by Rick Wanner (Version: 1)
11 comment(s)

ISC reader Scott has indicated that starting on December 27th he has seen a significant increase in Protocol 47 traffic being denied by his firewalls.  He has seen this traffic increasing from a baseline of near zero to 20,000 to 50,000 denies per day.  Protocol 47 traffic is not normally tracked by the ISC, so none of our sensors had detected this uptick.  However a little investigation reveals that firewalls I have access to are also seeing this increase. 

Protocol 47 is “GRE” (Generic Route Encapsulation) . It is commonly used as a Virtual Private Network (VPN). Essentially, GRE can be used to encapsulate any other protocol over IPv4. Sometimes it is used for IPv6 tunneling (instead of the more common IPv6 over IPv4, Protocol 41), and some anti-DDoS mitigation systems use it to route “cleaned” traffic.

I am showing this traffic originating from more than 100 unique sources.  I would like to dig deeper into this, but unfortunately I don't have access to packet captures to take a closer look at the traffic.  If you could let us know whether you are seeing the same thing, or better yet, have access to captures of this traffic, and could share it with us, it would be appreciated.

-- Rick Wanner MSISE - rwanner at isc dot sans dot edu - - Twitter:namedeplume (Protected)

Keywords: GRE
11 comment(s)
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