Category Archives: Miscellaneous

Anything and Everything

Disable Folder Redirection Synchronization

I came across this issue when we had an employee with a personal computer (that turned into a work computer) leave the company. I had to remove all the work applications and put the computer back to the state it was before we applied all the group policies and such to it.

As a side before we start, I know that I could just reformat the machine and then reinstall the drivers. But that just takes too long. Uninstalling 4 applications, removing the computer from the domain, and performing a few other tasks takes about 15 minutes to accomplish.

Here’s how to disable folder redirection with My Documents synchronization:
1.) Open MMC (Start >> Run >> MMC)
2.) Control M to add a module
3.) Alt D to add the snap-in module
4.) Navigate to Group Policy Object Editor (or a similar name)
5.) Click Add, and then finish (you’ll want it to be on the local machine anyway)
6.) Click Close, then OK
7.) Navigate to Local Computer Policy >> User Configuration >> Administrative Templates >> Network
8.) Disable Synchronize all offline files when loggin on, logging off, and before suspend.
9.) Reboot

Linux Show Hard Drive Lifetime Specs

This is a pretty cool tool I came across while doing research for another topic. Basically if you run Linux you can run this tool.

1.) sudo smartctl -a /dev/sda (or in my case it’s hda)

And that’s it. If it gives you an error, try running sudo smartctl by itself. If it says it requires tools to be installed, you can use apt-get install smartmontools.

This will give you all the details as reported by the SMART hardware system built into all newer drives. Total hours in use, power cycles, temperature, recovered errors, failures. Some of the data can be a little bit off (my initial reading of HD temperature was 705757226C) but overall it’s pretty neat.

Microsoft System Tools MRT SFC

Here are some hidden gems within the Microsoft Windows OS. I’m pretty sure these still apply to the newest Vista OS, but if not then it’s for XP ONLY.

Start >> Run >> “MRT”.
This will load up the Microsoft Removal Tool (Also known as Microsoft Windows Malicious Software Removal Tool). This will scan all of your files to see if some of the well-known Trojans or Viruses are loaded on your machine. This is NOT a replacement for AntiVirus software.

Start >> Run >> “SFC /SCANNOW”.
This will load up the System File Checker tool (Also known as Microsoft Windows XP Windows File Checker Version 5.1). This program will find all altered system files and fix them to the original. You’ll need a copy of your i386 folder (found on the Windows XP CD-ROM) in order to take full advantage of this tool.

Video Settings

I figured this might help someone, including myself.

Computers:
CGA: 320 x 200
QVGA: 320 x 240
VGA: 640 x 480
WVGA: 800 x 480
SVGA: 800 x 600
XGA: 1024 x 768
SXGA: 1280 x 1024
SXGA+: 1400 x 1050
UXGA (UGA): 1600 x 1200
WSXGA+: 1680 x 1050
WUXGA: 1920 x 1200
QXGA: 2048 x 1536
WQXGA: 2560 x 1600
QSXGA: 2560 x 2048
WQUXGA: 3840 x 2400

Television:
NTSC: 720 x 480
HD 720: 1280 x 720
HD 1080: 1920 x 1080

Secure Your Linux Box

Here are just a few small tricks to use to secure your linux based machines.

Disable Direct SSH Access For Root – Hackers must break or know TWO passwords to damage your system
1. SSH into your machine as root
2. cd /etc/ssh
3. nano /sshd_config
4. Under Authentication change PermitRootLogin to “no”
5. service sshd restart (Ubuntu is sudo /etc/init.d/ssh restart)

Slow Down SSH Attempts – This slows down attempts to no more than 3 per minute
1. SSH into your machine and su to root
2. iptables -I INPUT -p tcp –dport 22 -i eth0 -m state –state NEW -m recent –set
3. iptables -I INPUT -p tcp –dport 22 -i eth0 -m state –state NEW -m recent –update –seconds 60 –hitcount 4 -j DROP
4. iptables-save
5. iptables restart

[UPDATE 01.28.2008]
This requires a new(er) kernel with built-in support for the “recent” tag
1. SSH into your machine and su to root
2. iptables -N SSH_CHECK (this will create a new chain to lable all incoming SSH connections as SSH_CHECK)
3. iptables -A INPUT -p tcp –dport 22 -m state –state NEW -j SSH_CHECK (Checks the connection state port 22)
4. iptables -A SSH_CHECK -m recent –set –name SSH (labels the session type as SSH)
5. iptables -A SSH_CHECK -m recent –update –seconds 60 –hitcount 4 –name SSH -j DROP (Drops the connection if the hit counter reaches 4 in 60 seconds)

And then in Ubuntu
6. nano /etc/network/interfaces
7. After your eth0 or other network connection, add pre-up iptables-restore /etc/iptables.rules and post-down iptables-restore /etc/iptables.rules

[UPDATE 05.05.2009]
Running on Debian 5 this one works:
iptables -I INPUT -p tcp --dport 22 -i eth0 -m state --state NEW -m recent --set
iptables -I INPUT -p tcp --dport 22 -i eth0 -m state --state NEW -m recent --update --seconds 60 --hitcount 3 -j DROP

[UPDATE 01.06.2010]
Running on Ubuntu 9.10 this works:
iptables -I INPUT -p tcp --dport 22 -i eth0 -m state --state NEW -m recent --set
iptables -I INPUT -p tcp --dport 22 -i eth0 -m state --state NEW -m recent --update --seconds 240 --hitcount 3 -j DROP

This only allows 3 connection attempts (or successes) for every 6 minutes. Since my box is a small one that doesn’t require a lot of logins, I’d probably go even higher than this. Too high, though, and you could be locked out of your own box by others.

If you were to reboot your machine right now, your iptables configuration would disappear. Rather than type this each time you reboot, however, you can save the configuration, and have it start up automatically. To save the configuration, you can use iptables-save and iptables-restore.

[UPDATE 02.15.2010]
You can also limit based on username and IP address:

Limit based on Username:
nano /etc/ssh/sshd_config

PermitRootLogin no
AllowUsers userA userB@localhost userC@IPaddress

Limit based on IP address:
nano /etc/hosts.allow

sshd : localhost
sshd : 127.0.0.1
sshd : 192.168.0.0/24
sshd : localhost 127.0.0.1 192.168.1.* 172.16.34.253

nano /etc/hosts.deny

sshd : all

[UPDATE 08.31.2010]
You should probably make sure that your phpmyadmin and webmin installations are secured as well. It’s not hard to check the logs and see that there are many bots trying to gain access to these two installations – even if you don’t have them installed/configured on your box. Damn bots…

nano /etc/apache2/conf.d/phpmyadmin.conf

Obviously add your own IP’s into the config file. Then save the file and exit. Then restart apache.
apache2ctl restart