Wednesday, November 9, 2011

Snort gets a little help from swatch

Wanna know who is attacking your network and be notified ASAP? Maybe this setup might help you. Snort is a well developed open source IDS/IPS (intrusion detection/prevention system). An IDS is basically a sniffer (like tcpdump, wireshark, etc.) that looks at all the packets on the network and keeps an eye out for only interesting information. When it sees information that might be of interest (like a tcp port scan), it will log the packets pertaining to the port scan. An IDS will only log these packets, but doesn't take the extra steps to prevent the network attack from happening. An IPS will take the role of the IDS one step farther and has the ability to perform other actions in addition to logging. These might include blocking ports, setting firewall rules to block traffic based on port or ip address, etc.

Lets start using snort.

Snort can be used as a regular sniffer, like tcpdump. See the commands below:
# snort -dev -i eth0

To log the packets to a file, use the -l switch and specify a directory. Snort will create the file for you.
# snort -dev -i eth0 -l /root/snort/

Depending on your defaults, snort may log in Ascii mode or pcap mode. You can use the -K switch to specify (ascii, pcap or none).
# snort -K Ascii -dev -i eth0 -l /root/snort

To log packets in tcpdump format you can use the -b only.
# snort -b -dev -i eth0 -l /root/snort

Using snort as an IDS

This is accomplished by specifying a config file on the command line.
# snort -c snort.conf -i eth0

I always like to use -A for alert mode. Basically a file gets created called alerts, and when bad traffic is seen on the network, snort will make a note of it in this alert file. There are a few options for these, but i like using the fast option (see man snort for more details). Note that two files are created, the alert file and the snort.log file. The alert file will contain syslog like log entires when an attach happens and the snort log file will contain the bad traffic data(in tcpdump format if thats the option you went with) that triggered the alerts.
# snort -A fast -c snort.conf -i eth0

The snort.conf file is well doucmented and easy to configue. Here is a very barebones config file example.

var HOME_NET any
var AIM_SERVERS [,,,,,,,,]

include /etc/snort/classification.config

include $RULE_PATH/icmp.rules

The above example snort.conf will look for bad icmp traffic. If you ping your loopback interface, snort will generate some alerts and start logging this traffic.

How swatch can help you.

I blogged about swatch already so you can refer to my posting on that. Swatch can be used to monitor a snort alert file and be configured to send an email to you when a specific alert gets triggered. See the video below for a demonstration.

combining snort and swatch from aerokid240 on Vimeo.

One issue that will arise is that you may start recieving multiple emails. For example, if 4 ping packets were sent from the loopback address, then 4 alerts should be triggered by snort. Therefore, when swatch is notified about these alerts, 4 emails would be sent instead of just one. So if snort sets the same alert 100 times, you can expect 100 emails in this setup. I'm sure you can set swatch to run a script that would overcome this problem, but that is beyond what i wanted to demonstrate in this post.

Resources/Good Reading:

Tuesday, November 8, 2011

Uncloaking the unprotected with DirBuster

The following two paragraphs were taken from on DirBuster.

DirBuster is a multi threaded java application designed to brute force directories and files names on web/application servers. Often is the case now of what looks like a web server in a state of default installation is actually not, and has pages and applications hidden within. DirBuster attempts to find these.

However tools of this nature are often as only good as the directory and file list they come with. A different approach was taken to generating this. The list was generated from scratch, by crawling the Internet and collecting the directory and files that are actually used by developers! DirBuster comes a total of 9 different lists (Further information can be found below), this makes DirBuster extremely effective at finding those hidden files and directories. And if that was not enough DirBuster also has the option to perform a pure brute force, which leaves the hidden directories and files nowhere to hide! If you have the time ;)

Here is a video that i've created illustrating one of the ways DirBuster can be used and why its very important to take the necessary steps to secure your data, rather than just hiding it. Because the webmaster didn't properly configure his webserver for security, it was possible to gain access to some data.

Dirbuster from aerokid240 on Vimeo.

Resources / Good Reading:

Saturday, November 5, 2011

Brute forcing html login forms

Lately, i been really busy at work and havent researched or read any books in the past two weeks. Already i felt like my brain was slipping away. So i decided to fire up a DVL (Damn Vulnerable linux), which is a live distribution that has many vulnerabilities for one to practice their security skills. I haven't used it before so i didn't know what i was getting into. I did a port scan and found two open ports (631 and 3306/mysql). Initially, i tried to identify the MySQL version using metasploit but that didn't work. I then tried using the metasploit mysql bruteforcer, to do a dictionary attack on the service, but metasploit complained that the attack will only work on older versions of MySQL. I was clueless. I began looking around the DVL and then started apache (isn't running by default) from the desktop shortcuts. I went back to my attacking backtrack 5 machine and fired up Firefox then went to the relevant webpage URL for the DVL machine. Interesting enough, it gave me a directory listing. I saw phpmyadmin listed so i decided to go in their. I was presented with the login page. I tried some random stuff i thought might work and had no success. I was failing miserably. What i needed to do at that point was automate the password guessing process. This is where hydra comes in.

This is the code i used.
# hydra -l admin -P passwords.lst -e ns -vV http-post-form "/phpmyadmin/index.php:pma_username=^USER^&pma_password=^PASS^&server=1:denied"

After a few minutes, i had a smile on my face. Hydra found two usable passwords for the username admin. Just to avoid any spoilers, i wouldn't post the relevant passwords. Out of curiosuty, i decided to run hydra again for the user root.

# hydra -l root -P passwords.lst -f -e ns -vV http-post-form "/phpmyadmin/index.php:pma_username=^USER^&pma_password=^PASS^&server=1:denied"

I decided to use the "-f" switch so hydra would quit immediately when a matching password is found. Indeed, after a few seconds, i had a usable password. In reality, there is nothing to fancy about this as the accounts and their passwords seem to be at their defaults and if you knew what mysql accounts default credentials are, then you know that bruteforcing here was a dead waste of time :). Either way, i had a foot in the door and the point of this was to demonstrate how you can bruteforce html login forms with hydra.

BTW, adding the "-U" switch would give you usage information when using the "http-post-form" service.

Update: It turns out that you can use any username with the password of "0" for some reason :). Now that you have access, to the mysql database, you can snoop around to get information and user logins for web apps like wordpress and joomla.

Resources/Good Reading: