Snort - the de facto standard for intrusion detection/prevention
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Directives

Table: Config Directives
Command Example Description
order config order: pass alert log activation Changes the order that rules are evaluated.
alertfile config alertfile: alerts Sets the alerts output file.
classification config classification: misc-activity,Misc activity,3 See Table [*] for a list of classifications.
dump_chars_only config dump_chars_only Turns on character dumps (snort -C).
dump_payload config dump_payload Dumps application layer (snort -d).
decode_data_link config decode_data_link Decodes Layer2 headers (snort -e).
bpf_file config bpf_file: filters.bpf Specifies BPF filters (snort -F).
daemon config daemon Forks as a daemon (snort -D).
interface config interface: xl0 Sets the network interface (snort -i).
alert_with_interface_name config alert_with_interface_name Appends interface name to alert (snort -I).
logdir config logdir: /var/log/snort Sets the logdir (snort -l).
umask config umask: 022 Sets umask when running (snort -m).
pkt_count config pkt_count: 13 Exits after N packets (snort -n).
nolog config nolog Disables logging. Note: Alerts will still occur. (snort -N).
obfuscate config obfuscate Obfuscates IP Addresses (snort -O).
no_promisc config no_promisc Disables promiscuous mode (snort -p).
quiet config quiet Disables banner and status reports (snort -q).
chroot config chroot: /home/snort Chroots to specified dir (snort -t).
checksum_mode config checksum_mode : all Types of packets to calculate checksums. Values: none, noip, notcp, noicmp, noudp, ip, tcp, udp, icmp or all.
checksum_drop config checksum_drop : all Types of packets to drop if invalid checksums. Values: none, noip, notcp, noicmp, noudp, ip, tcp, udp, icmp or all (only applicable in inline mode and for packets checked per checksum_mode config option).
set_gid config set_gid: 30 Changes GID to specified GID (snort -g).
set_uid set_uid: snort_user Sets UID to $<$id$>$ (snort -u).
utc config utc Uses UTC instead of local time for timestamps (snort -U).
verbose config verbose Uses verbose logging to STDOUT (snort -v).
dump_payload_verbose config dump_payload_verbose Dumps raw packet starting at link layer (snort -X).
show_year config show_year Shows year in timestamps (snort -y).
stateful config stateful Sets assurance mode for stream4 (est). See the stream4_reassemble configuration in table [*].
min_ttl config min_ttl:30 Sets a Snort-wide minimum ttl to ignore all traffic.
disable_decode_alerts config disable_decode_alerts Turns off the alerts generated by the decode phase of Snort.
disable_tcpopt_experimental_
alerts
config disable_tcpopt_experiment
al_alerts
Turns off alerts generated by experimental TCP options.
disable_tcpopt_obsolete_
alerts
config disable_tcpopt_obsole
te_alerts
Turns off alerts generated by obsolete TCP options.
disable_tcpopt_ttcp_alerts config disable_tcpopt_ttcp_alerts Turns off alerts generated by T/TCP options.
disable_ttcp_alerts config disable_ttcp_alerts Turns off alerts generated by T/TCP options.
disable_tcpopt_alerts config disable_tcpopt_alerts Disables option length validation alerts.
disable_ipopt_alerts config disable_ipopt_alerts Disables IP option length validation alerts.
enable_decode_drops config enable_decode_drops Enables the dropping of bad packets identified by decoder (only applicable in inline mode).
enable_tcpopt_experimental_
drops
config enable_tcpopt_experi
mental_drops
Enables the dropping of bad packets with experimental TCP option. (only applicable in inline mode).
enable_tcpopt_obsolete_
drops
config enable_tcpopt_obsole
te_drops
Enables the dropping of bad packets with obsolete TCP option. (only applicable in inline mode).
enable_tcpopt_ttcp_drops enable_tcpopt_ttcp_drops Enables the dropping of bad packets with T/TCP option. (only applicable in inline mode).
enable_tcpopt_drops config enable_tcpopt_drops Enables the dropping of bad packets with bad/truncated TCP option (only applicable in inline mode).
enable_ipopt_drops config enable_ipopt_drops Enables the dropping of bad packets with bad/truncated IP options (only applicable in inline mode).
flowbits_size config flowbits_size: 128 Specifies the maximum number of flowbit tags that can be used within a rule set.
event_queue config event_queue: max_queue 512 log 100 order_events priority Specifies conditions about Snort's event queue. You can use the following options:
  • max_queue $<$integer$>$ (max events supported)
  • log $<$integer$>$ (number of events to log)
  • order_events [priority$\vert$content_length] (how to order events within the queue)
See Section [*] for more information and examples.
layer2resets config layer2resets: 00:06:76:DD:5F:E3 This option is only available when running in inline mode. See Section [*].
detection config detection: search-method ac no_stream_inserts max_queue_events 128 Makes changes to the detection engine. The following options can be used:
  • search-method $<$ac $\vert$ ac-std $\vert$ ac-bnfa $\vert$ acs $\vert$ ac-banded $\vert$ ac-sparsebands $\vert$ lowmem $>$
    • ac Aho-Corasick Full (high memory, best performance)
    • ac-std Aho-Corasick Standard (moderate memory, high performance)
    • ac-bnfa Aho-Corasick NFA (low memory, high performance)
    • acs Aho-Corasick Sparse (small memory, moderate performance)
    • ac-banded Aho-Corasick Banded (small memory, moderate performance)
    • ac-sparsebands Aho-Corasick Sparse-Banded (small memory, high performance)
    • lowmem Low Memory Keyword Trie (small memory, low performance)
  • no_stream_inserts
  • max_queue_events$<$integer$>$
asn1 config asn1:256 Specifies the maximum number of nodes to track when doing ASN1 decoding. See Section [*] for more information and examples.
snaplen config snaplen: 2048 Set the snaplength of packet, same effect as -P $<$snaplen$>$ or -snaplen $<$snaplen$>$ options.
read_bin_file config read_bin_file: test_alert.pcap Specifies a pcap file to use (instead of reading from network), same effect as -r $<$tf$>$ option.
reference config reference: myref http://myurl.com/?id= Adds a new reference system to Snort.
ignore_ports config ignore_ports: udp 1:17 53 Specifies ports to ignore (useful for ignoring noisy NFS traffic). Specify the protocol (TCP, UDP, IP, or ICMP), followed by a list of ports. Port ranges are supported.


next up previous contents
Next: Preprocessors Up: Config Previous: Format   Contents
Steven Sturges 2006-12-08