Snort UDP traffic in loopback interface

[evalues evalues <evalues.es () gmail com>]

Hi, when I set Snort to listen in Loopback interface it doesn’t trigger
alerts for UDP rules. The same rules in eth0 interface work perfectly.
Besides, TCP and ICMP alerts also work in Loopback interface.

If I run Snort in sniffer mode I can view the datagram, but the alerts are
not triggered. This is an example of an SNMP datagram that should raise an
alert:

(snort decoder) WARNING: Bad Traffic Same Src/Dst IP (snort decoder)
WARNING: Bad Traffic Loopback IP 12/11-07:37:30.785801 00:00:00:00:00:00 –>
00:00:00:00:00:00 type:0x800 len:0x59 127.0.0.1:59796 –> 127.0.0.1:162 UDP
TTL:64 TOS:0x0 ID:0 IpLen:20 DgmLen:75 DF Len: 47 0x0000: 00 00 00 00 00 00
00 00 00 00 00 00 08 00 45 00 …………..E. 0x0010: 00 4B 00 00 40 00 40 11 3C
A0 7F 00 00 01 7F 00 .K..@.@.<……. 0x0020: 00 01 E9 94 00 A2 00 37 FE 4A 30
2D 02 01 00 04 …….7.J0-…. 0x0030: 09 56 69 73 69 74 61 6E 74 65 A4 1D 06 07
2B 06 .Visitante….+. 0x0040: 01 04 01 96 26 40 04 7F 00 01 01 02 01 06 02
01 ….&@………. 0x0050: 01 43 04 04 9E 5A F2 30 00 .C…Z.0.

=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+

Can someone help me?

Thank you very much.

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