Security

About: The way that pretty much all pc’s are hacked is by gathering info, then finding a security bug. By reading this I hope you’ll learn how much info. can be obtained from your server, and hopefully how to stop it.
I’m repeatedly getting blank e-mails to my Outlook (don’t laugh) inbox. I right click, choose properties and look at the message source. The following interesting information is included :
Received: from AspEmail ([66.200.114.146])
I recognize the numbers as an IP, and Asp as the Windows equivalent of Php, which normally runs on NT servers.

Stopping the most common attack:

Ok well, one of the easiest ways of getting superuser access is through anonymous ftp access into a webpage. This can easily be secured against. First, you need to learn a little about the password file…

root:User:d7Bdg:1n2HG2:1127:20:Superuser 
TomJones:p5Y(h0tiC:1229:20:Tom Jones,:/usr/people/tomjones:/bin/csh 
BBob:EUyd5XAAtv2dA:1129:20:Billy Bob:/usr/people/bbob:/bin/csh

This is an example of a regular encrypted password file. The Superuser is the part that gives you root. That’s the main part of the file.

Key and text
Xor encryption uses a key(password) to encrypt text. Ascci
All letters/symbols/numbers are represented by a number from 0 to 256. This is called the ASCII number.
Binary
In an XOR encryption program each letter of the key and the text are converted to ASCII, then to binary (0’s and 1’s).
XORing
The 0 or 1 from the key is XORed against the 0 or 1 of the text. If the key is shorter than the text, is repeats. XORing a 0 against a 0 gives a 1. See the below truth table for all

Practically all UNIX-based servers run a SSH server to allow remote administration across the Internet. From time to time, you might notice a large number of failed login attempts. Often, these are brute-force attacks against your SSH server

In this hack, we’ll show you 5 tips to protect machines running SSH daemons from brute-force attacks.

Change the default port

Configure your SSH daemon to listen on a non-standard port. SSH servers have no trouble doing this. Just make sure you configure your firewalls to allow connections to the new port. For instance, to have your SSH daemon to accept connections on port 2222, edit the sshd_config file and modify the value of Port to 2222 and restart the SSH daemon.

Perl is the main server scripting language for web servers. It is used because of its ease of use and its power, but because of the ease of use, a power perl can be exploited. This document will tell you how to secure your web server from attacks.

Perl scripts can be identified by the outside world as they normally have .pl or .cgi extensions.
Tainting
IF you have ever seen a perl script, you will have noticed that on the first line there is the path to the perl program. eg:
#!/usr/local/bin/perl -w
The -w tells perl to give warnings if there are errors in the code. The security equivalent is to disallow insecure commands from user input. The way this works is that user input cannot execute a command, but any variable created in the script can. eg;
$input= ; STDIN is from the user, so it is considered as insecure
$untainted = "hi";
To enable this secure mode (or tainting, to call it its proper name) add -t to the line, eg; #!/usr/local/bin/perl -T or #!/usr/local/bin/perl -Tw
You can untaint a variable by putting the data it contains into a variable name $number, e.g. $input = $1; The following perl script parses user input if it doesn’t contain dangerous characters tells perl it is secure: