Agora que já configuramos basicamente o PSAD, vamos inicializá-lo:

# /etc/init.d/psad start
Starting the psad daemons.

Os seguintes daemons fazem parte do psad:

• /usr/bin/perl -w /usr/sbin/psad
• /usr/sbin/psadwatchd
• /usr/sbin/kmsgsd

Agora ele está executando e protegendo nosso sistema.

Vamos realizar um teste com o nmap localmente:

# nmap -sT -v -PT localhost
Starting nmap 3.70 ( http://www.insecure.org/nmap/ ) at 2004-09-01 17:29 BRT
Note: Host seems down. If it is really up, but blocking our ping probes, try -P0
Nmap run completed -- 1 IP address (0 hosts up) scanned in 2.150 seconds

BINGO, como vimos não retornou nenhuma porta válida, agora vamos ver os emails:

# mail
"/var/spool/mail/root": 12 messages 1 new 12 unread
U 1 root@unsekurity.lo Wed Sep 1 17:27 52/1715 [psad-alert] DL2 src: loc
U 2 root@unsekurity.lo Wed Sep 1 17:27 52/1715 [psad-alert] DL2 src: loc
?1
Message 1:
From root@unsekurity.local Wed Sep 1 17:27:07 2004
X-Original-To: root@localhost
Delivered-To: root@localhost.unsekurity.local
Date: Wed, 01 Sep 2004 17:27:06 -0300
To: root@localhost.unsekurity.local
Subject: [psad-alert] DL2 src: localhost dst: localhost
User-Agent: nail 10.5 4/27/03
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
From: root@unsekurity.local (root)

=-=-=-=-=-=-=-=-=-=-=-= Wed Sep 1 17:27:06 2004 =-=-=-=-=-=-=-=-=-=-=-=

         Danger level: [2] (out of 5) Multi-Protocol

    Scanned tcp ports: [4-6112: 22 packets]
            tcp flags: [SYN: 22 packets, Nmap: -sT or -sS]
  Iptables chain: INPUT (prefix "Port Scan Attack"), 22 packets
    Scanned udp ports: [512: 1 packets, Nmap: -sU]
       Iptables chain: INPUT (prefix "Port Scan Attack"), 1 packets

               Source: 127.0.0.1
                  DNS: localhost

          Destination: 127.0.0.1
                  DNS: localhost

      Syslog hostname: RootSec

     Current interval: Wed Sep  1 17:27:01 2004 (start)
                       Wed Sep  1 17:27:06 2004 (end)

   Overall scan start: Wed Sep  1 17:26:40 2004
   Total email alerts: 5
   Complete tcp range: [4-44443]
   Complete udp range: [512]

   chain:   interface:   tcp:   udp:   icmp:  
   INPUT    lo           161    4      0      

[+] Whois Information:
Unknown AS number or IP network. Please upgrade this program.

?q

Como vimos ele detalhou o ataque: tipo de scan, protocolos utilizados e etc.

Vamos ver o syslog também:

# tail /var/log/messages
Sep 1 17:28:00 RootSec kernel: Port Scan AttackIN=lo OUT= MAC=00:00:00:00:00:00:00:00:00:00:00:00:08:00 SRC=127.0.0.1 DST=127.0.0.1 LEN=39 TOS=0x00 PREC=0x00 TTL=64 ID=0 DF PROTO=UDP SPT=32771 DPT=512 LEN=19
Sep 1 17:28:01 RootSec kernel: Port Scan AttackIN=lo OUT= MAC=00:00:00:00:00:00:00:00:00:00:00:00:08:00 SRC=127.0.0.1 DST=127.0.0.1 LEN=40 TOS=0x00 PREC=0x00 TTL=39 ID=45715 PROTO=TCP SPT=54369 DPT=1427 WINDOW=4096 RES=0x00 SYN URGP=0
Sep 1 17:28:05 RootSec psad: scan detected: 127.0.0.1 -> 127.0.0.1 tcp=[142-1427] SYN tcp=2 udp=1 icmp=0 dangerlevel: 2
Sep 1 17:28:05 RootSec psad: sending email alert to: root@localhost
Sep 1 17:28:32 RootSec kernel: Port Scan AttackIN=ppp0 OUT= MAC= SRC=200.176.2.10 DST=200.232.209.247 LEN=115 TOS=0x00 PREC=0x00 TTL=53 ID=0 DF PROTO=UDP SPT=53 DPT=32776 LEN=95

O PSAD além de reportar com grande precisão o ataque, não permitiu que o atacante pudesse coletar informações sobre nosso servidor.