Itx8071-task2

This homework assignment requires the knowledge from Modules 6 and 7.

Create SEC rules that accomplish the following event correlation task:

1) The rules must process netfilter firewall syslog events about blocked packets. For example, the following two events represent two packets from host 192.168.1.67 which were blocked by the local firewall:

Oct 25 01:13:02 localhost kernel: iptables: IN=eth0 OUT= MAC=X SRC=192.168.1.67 DST=192.168.1.107 
  LEN=60 TOS=0x10 PREC=0x00 TTL=64 ID=20049 DF PROTO=TCP SPT=44963 DPT=23 WINDOW=49640 RES=0x00 SYN URGP=0 
Oct 25 01:13:08 localhost kernel: iptables: IN=eth0 OUT= MAC=X SRC=192.168.1.67 DST=192.168.1.107 
  LEN=60 TOS=0x10 PREC=0x00 TTL=64 ID=36362 DF PROTO=TCP SPT=56918 DPT=25 WINDOW=29200 RES=0x00 SYN URGP=0 

The rules must also process Apache web server syslog events with status codes 401 (Unauthorized), 403 (Forbidden), 404 (Not Found), and 405 (Method Not Allowed). For example, the following event represents GET request from client 192.168.1.101 to URL /banner.png that was not found (status code is 404):

Nov  6 19:05:37 localhost apache: 192.168.1.101 - - [06/Nov/2016:19:05:37 +0200] "GET /banner.png HTTP/1.1" 404 208 "-" 
  "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.71 Safari/537.36"

2) if netfilter firewall blocked packet events and/or Apache events with 401 status codes have been seen from the same host repeatedly during 5 minutes, so that time between two successive events does not exceed 60 seconds, memorize that host for the following 1 hour as suspicious host (the time between the last event and the end of the 5-minute window must also not exceed 60 seconds).

For example, if the following events appear for host 10.1.1.7, this host should be memorized as suspicious, since in 5-minute window from 12:30:06 to 12:35:06 six events have been seen which are separated from each other by no more than 60 seconds (time gaps between events are 59, 55, 52, 58, and 51 seconds, while the gap between the last event and the end of the 5-minute window is 25 seconds).

Nov 15 12:30:06 localhost kernel: iptables: IN=eth0 OUT= MAC=X SRC=10.1.1.7 DST=10.13.25.59 
  LEN=60 TOS=0x00 PREC=0x00 TTL=62 ID=1881 DF PROTO=TCP SPT=16333 DPT=21 WINDOW=5840 RES=0x00 SYN URGP=0
Nov 15 12:31:05 localhost kernel: iptables: IN=eth0 OUT= MAC=X SRC=10.1.1.7 DST=10.13.25.59 
  LEN=60 TOS=0x00 PREC=0x00 TTL=62 ID=23421 DF PROTO=TCP SPT=34342 DPT=23 WINDOW=29200 RES=0x00 SYN URGP=0
Nov 15 12:32:00 localhost kernel: iptables: IN=eth0 OUT= MAC=X SRC=10.1.1.7 DST=10.13.25.59 
  LEN=60 TOS=0x00 PREC=0x00 TTL=62 ID=31442 DF PROTO=TCP SPT=47846 DPT=25 WINDOW=49640 RES=0x00 SYN URGP=0
Nov 15 12:32:52 localhost apache: 10.1.1.7 - - [15/Nov/2017:12:32:52 +0200] "GET / HTTP/1.1" 401 489
Nov 15 12:33:50 localhost kernel: iptables: IN=eth0 OUT= MAC=X SRC=10.1.1.7 DST=10.13.25.59 
  LEN=60 TOS=0x00 PREC=0x00 TTL=62 ID=17209 DF PROTO=TCP SPT=11652 DPT=143 WINDOW=7290 RES=0x00 SYN URGP=0
Nov 15 12:34:41 localhost apache: 10.1.1.7 - - [15/Nov/2017:12:34:41 +0200] "GET / HTTP/1.1" 401 489

3) if some host has been previously memorized as suspicious, and 3 Apache events with status codes 403, 404 and/or 405 are observed from this host within 60 seconds, so that HTTP method is different for all events, send an e-mail about the offending host to root@localhost.

Note that the detection should be done with a sliding window approach -- if the counting operation for some host has not seen enough events during 60 seconds, the 60 second detection window should be moved forward.

After an e-mail alert has been issued about the host, disable further alerts for this host for 3 hours.

For example, suppose the following events are observed and the host 192.168.56.1 has been previously memorized as suspicious:

Nov 15 13:46:12 localhost apache: 192.168.56.1 - - [15/Nov/2017:13:46:12 +0200] "GET / HTTP/1.1" 200 4897 "-" 
  "curl/7.29.0"
Nov 15 13:46:31 localhost apache: 192.168.56.1 - - [15/Nov/2017:13:46:31 +0200] "GET /test.html HTTP/1.1" 404 207 "-" 
  "curl/7.29.0"
Nov 15 13:46:33 localhost apache: 192.168.56.1 - - [15/Nov/2017:13:46:33 +0200] "GET /test.html HTTP/1.1" 404 207 "-" 
  "curl/7.29.0"
Nov 15 13:46:41 localhost apache: 192.168.56.1 - - [15/Nov/2017:13:46:41 +0200] "PUT /test.html HTTP/1.1" 405 230 "-" 
  "curl/7.29.0"
Nov 15 13:46:42 localhost apache: 10.1.17.3 - - [15/Nov/2017:13:46:42 +0200] "GET / HTTP/1.1" 200 4897 "-" 
  "Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0"
Nov 15 13:46:47 localhost apache: 192.168.56.1 - - [15/Nov/2017:13:46:47 +0200] "DELETE /index.html HTTP/1.1" 405 234 "-" 
  "curl/7.29.0"

The event correlation rules must produce an alarm at Nov 15 13:46:47 about offending host 192.168.56.1, since this host has used three different HTTP methods (GET, PUT, and DELETE) within 60 seconds, so that HTTP status codes are either 403, 404, or 405. Note that the event at Nov 15 13:46:12 should be ignored, since its status code is 200.

Some hints for accomplishing this assignment:

• don't try to solve the whole assignment with just one rule, but rather write several rules which interact,
• in order to accomplish subtask 2 (detection of 5 minute event sequence with max 60 second intervals), use Single rules that set up contexts with specific actions-on-expire.

Apart from studying the examples from the course slides, have a look at the SEC man page (installed at the virtual machines or found at http://simple-evcorr.github.io/man.html).