encrypt file.txt to file.enc using 256-bit AES in CBC mode

openssl enc -aes-256-cbc -salt -in file.txt -out file.enc

the same, only the output is base64 encoded for, e.g., e-mail

openssl enc -aes-256-cbc -a -salt -in file.txt -out file.enc

decrypt binary file.enc

openssl enc -d -aes-256-cbc -in file.enc

decrypt base64-encoded version

openssl enc -d -aes-256-cbc -a -in file.enc

thanks Mark, http://bolusmjak.posterous.com/

to begin to properly secure your linux computer with ssh your sshd configuration file should contain the lines below.  These lines prevent root access, force public key authentication (no password to crack) and restrict access to named users only.

PermitRootLogin no

PasswordAuthentication no

RSAAuthentication yes

PubkeyAuthentication yes

AllowUsers babyman evan

touch temp -t 200910011130

touch ntemp -t 200910011630

find / -cnewer temp -and ! -cnewer ntemp

use the following to set the time between when screen saver activates and when a password is required to access the computer, the time is in seconds (10 in this case)

defaults -currentHost write com.apple.screensaver askForPasswordDelay -int 10

place your mat on the floor and unroll it, do not drop it, that huge CRACK! is not cool, ever!!! (for more on cracks see tip #1). If you are taking a hot yoga class try rolling your towel up in your mat when you're preparing your stuff the night before.

nmap -sT -O localhost

netstat -an

lsof -i

the following command will sort and show all of the rpm packages installed on a computer using less

rpm -qa | sort | less

ever wonder what the IP address of that server in the corner is, you could always try scanning your network for computers using nmap.

sudo apt-get install nmap

to scan for running computers, here using sudo is optional but will provide more information, all others require root privileges

<sudo> nmap -sP 192.168.1.1/24

to scan for open ports on a computer

sudo nmap -sS 192.168.1.1/24

to include open ports and operating system information

sudo nmap -O 192.168.1.1/24