[Oisf-users] Suricata not detecting app-layers

Joris Roefs l Onsight Solutions BV joris.roefs at onsight.nl
Tue Dec 23 14:14:34 UTC 2014

Hi list,

Suricata is giving me a hard time alerting on app-layer specific traffic. I want to alert on specific HTTP and DNS events, but so far I don't get any events at all.
For debugging purposes I've created an alert that will fire on every http session. There hasn't been a hit yet, although I'm monitoring my company's internet connection and have initiated enough HTTP-requests. Tcpdump shows me  the complete HTTP-session and when I use an alert that fires on any tcp-session over HTTP_PORTS I get to see them as well.
alert http any any -> any any (msg:"HTTP connection detected "; sid:89601; rev:1;)
alert tcp $HOME_NET any -> $EXTERNAL_NET $HTTP_PORTS (msg:"Outgoing HTTP connection detected "; sid:89602; rev:1;)
So, first one never firing, second one constantly. Should be the other way 'round, right?

Anyone any idea what could be wrong here (or better: where did I go wrong?)?

Some additional information:

-       Checksum checks are off in suricata and offloading is disabled on the sniffing interface.

-       We're in IDS mode, on a SPAN port, which is not overloaded.

-       Stats.log says no checksum issues, no reassembly issues,

-       Configs attached

-       Build information:
$> suricata --build-info
This is Suricata version 2.0.4 RELEASE
SIMD support: SSE_4_2 SSE_4_1 SSE_3
Atomic intrisics: 1 2 4 8 byte(s)
32-bits, Little-endian architecture
GCC version 4.7.2, C version 199901
L1 cache line size (CLS)=64
compiled with LibHTP v0.5.15, linked against LibHTP v0.5.15
Suricata Configuration:
  AF_PACKET support:                       yes
  PF_RING support:                         no
  NFQueue support:                         no
  NFLOG support:                           no
  IPFW support:                            no
  DAG enabled:                             no
  Napatech enabled:                        no
  Unix socket enabled:                     yes
  Detection enabled:                       yes

  libnss support:                          yes
  libnspr support:                         yes
  libjansson support:                      yes
  Prelude support:                         no
  PCRE jit:                                yes
  LUA support:                             no
  libluajit:                               no
  libgeoip:                                yes
  Non-bundled htp:                         no
  Old barnyard2 support:                   no
  CUDA enabled:                            no

  Suricatasc install:                      yes

  Unit tests enabled:                      no
  Debug output enabled:                    no
  Debug validation enabled:                no
  Profiling enabled:                       no
  Profiling locks enabled:                 no
  Coccinelle / spatch:                     no

Generic build parameters:
  Installation prefix (--prefix):          /usr
  Configuration directory (--sysconfdir):  /etc/suricata/
  Log directory (--localstatedir) :        /var/log/suricata/

  Host:                                    i686-pc-linux-gnu
 GCC binary:                              gcc
  GCC Protect enabled:                     no
  GCC march native enabled:                yes
  GCC Profile enabled:                     no

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