[Oisf-users] Ignore ips in rule

[Xavier Romero]

Hello,

I've this custom rule:

...
alert udp [$EXTERNAL_NET,!$GOOGLE_DNS] 53 -> [$HOME_NET,!$DNS_SERVERS] any (msg:"Possible atac DNS"; threshold: type both, track by_dst, count 600, seconds 60; classtype:attempted-dos; sid:101111009; rev:5;)
...


And this definition on suricata.yaml:

...
# Holds variables that would be used by the engine.
vars:

  # Holds the address group vars that would be passed in a Signature.
  # These would be retrieved during the Signature address parsing stage.
  address-groups:

    HOME_NET: "[x.x.x.x/24]"

    GOOGLE_DNS: "[8.8.8.8,8.8.4.4]"

    EXTERNAL_NET: "!$HOME_NET"

    HTTP_SERVERS: "$HOME_NET"

    SMTP_SERVERS: "$HOME_NET"

    SQL_SERVERS: "$HOME_NET"

    DNS_SERVERS: "[a.a.a.a,b.b.b.b,c.c.c.c,d.d.d.d]"

    TELNET_SERVERS: "$HOME_NET"
...

However, there are alerts like these:
...
08/27/2014-10:33:37.344581  [**] [1:101111009:5] Possible atac DNS [**] [Classification: Attempted Denial of Service] [Priority: 2] {UDP} 8.8.8.8:53 -> a.b.c.d:52721
08/27/2014-10:33:48.511591  [**] [1:101111009:5] Possible atac DNS [**] [Classification: Attempted Denial of Service] [Priority: 2] {UDP} 8.8.8.8:53 -> a.b.c.d:35899
...

I'm expecting to totally ignore packets whith IP source 8.8.8.8. What I'm doing wrong?

I've also tried
  [$EXTERNAL_NET,![8.8.8.8,8.8.4.4]]
Instead of:
 [$EXTERNAL_NET,!$GOOGLE_DNS]
With the same result.

Each time I modify the rule, I increment REV number and restart suricata.

Thank you very much,
Xavier Romero
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