Security and Privacy in a Networked World/Too easy to misuse

Nothing special

Hollywood movies tend to suggest that it takes Dr. Evil or some other nasty genius to be a cybercriminal. While some of it may be true for some kinds of attacks as well as for some well-defended targets, it is surprisingly simple to achieve significant results. Today's topic was inspired by the book Violent Python by TJ O'Connor - but similar easy recipes can also be found online.

But first, we need to learn a bit more about Python.

Python (continued)

Strings

Manipulation of strings (textual values) is a common task for security-related scripts in Python - e.g. a web page URL (web address), an IP address or a serial number are all handled as strings. Finding, extracting and relocating substrings (e.g. replace the last block of an IP address with another) are all common.

A typical example is checking if a substring exists in a longer expression:

signature = "MyServer version 5.05 Enterprise edition"
target = "5.05"
if (target in signature):
  print "This version can be attacked"
else:
  print "This server is secure"

READ MORE at http://docs.python.org/2/library/stdtypes.html#string-methods

Modules

One of the strong points of Python is modularity - in addition to the pretty extensive standard library, one can link specific modules to his/her program to access a multitude of additional functions. The modules are linked to the program using the "import" directive:

socket

This module contains many handy tools to handle networking. While the full description is available here, let us just stop at some simple uses:

• socket.socket() - in simple terms, defines a new network connection. To connect to a specific IP address and port, we need to define a connection to a variable. The following example defines a variable "netcon" and creates a connection to an FTP port of a local network computer:

import socket
netcon = socket.socket()
netcon.connect("192.168.1.10", 21)

• recv() - asks for a given number of bytes from an open connection. E.g. the previous example may be added something like this:

import socket
netcon = socket.socket()
netcon.connect("192.168.1.10", 21)
reply = netcon.recv(1024)
if ("Old FTP server SomeOldVersion" in reply):
   print "A good target!"
else:
   print "Sorry, no luck."

Note: some servers would refuse to answer but many will do it. Typically, the first kilobyte (1024 bytes) of the reply will contain some information about the server - and in many cases, this includes the name and version of the software in use. Now, combining this with a known vulnerability database like SecurityFocus may produce a lot of possibilities.

Also, most web servers tend to refuse connection or ignore it, resulting in timeout. However, other services (SSH, FTP, e-mail servers) are often more revealing.

Functions

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Some examples

Simple port scanner

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Archive password cracker

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