mod_rewrite, a beginner’s guide (with examples)

Until recently, I only had the vaguest of ideas of what mod_rewrite was, and I certainly had no clue about how to use it. So, when I started designing this site, I decided to delve into the wonders that are the mod_rewrite Apache module.

So, what is mod_rewrite for?

Simply, mod_rewrite is used for rewriting a URL at the server level, giving the user output for that final page. So, for example, a user may ask for http://www.somesite.com/widgets/blue/, but will really be given http://www.somesite.com/widgets.php?colour=blue by the server. Of course, the user will be none the wiser to this little bit of chicanery.

On workingwith.me.uk, I use mod_rewrite to redirect all pages to one central PHP page, which then loads the data that the user wanted from an external data file. Lots of people use mod_rewrite to show an “alternative” image when people are hotlinking directly to their images.

Protecting Your Data: A Guide to Windows Firewall

Introduction to Windows Firewall

The introduction of high-speed Internet connectivity has created a powerful and extraordinary computer networking experience. This newfound burst of bandwidth has launched new innovations in information exchange, media access, and other advanced computing experiences. Unfortunately, this technology has also created a very accessible conduit to the internals of your computer. Using these open and available digital pipelines, it’s now easier than ever for hackers, worms, and viruses to attack your unprotected home and home office computers.

These threats aren’t exaggerations thrown around by computer industry pundits or descriptions of theoretical worst-case scenarios. A test in my lab found that a computer added onto a previously unconnected cable-modem connection was found by automated hacker tools in three minutes, attacked by an Internet worm in eleven minutes, and it only took five hours before a hacker was running active scans against my computer in an attempt to find an open doorway or unlocked pathway into my system.

These timeframes are staggering. If an unprotected computer is connected to your high-speed Internet connection then your confidential information, financial details, private email messages, and any other personal information on your computer is at risk. If you connect to the Internet in hotels or wireless hot-spots without a personal firewall, then your computer and private information can be easily attacked.

Will an nmap Operating System scan work through a firewall?

From the mailbag, Jesse C. writes:

I have been assigned a project within my organization to perform OS Fingerprinting on subnets. What I find is that end-users that do not use Windows Firewall (have it disabled or not installed), I am able to detect their OS with no problem. The problem lies that many new users have Windows SP2 Firewall enabled which are limiting my scan results. I am using the following nmap command in Linux. (# nmap -sS -O -PI 192.168.0.1/24)What should I do to accurately perform an OS Fingerprint scan on my subnet? If not 100% accurate, what nmap commands would your suggest?

Jesse –

MPLS Overview

Multi-Protocol Label Switching (MPLS) defines a mechanism for packet forwarding in network routers. It was originally developed to provide faster packet forwarding than traditional IP routing, although improvements in router hardware have reduced the importance of speed in packet fowarding. However, the flexibility of MPLS has led to it becoming the default way for modern networks to achieve Quality of Service (QoS), next generation VPN services, and optical signaling.

Traditional IP networks are connectionless: when a packet is received, the router determines the next hop using the destination IP address on the packet alongside information from its own forwarding table. The router’s forwarding tables contain information on the network topology. They use an IP routing protocol, such as OSPF, IS-IS, BGP, RIP or static configuration, to keep their information synchronized with changes in the network.

MPLS also uses IP addresses, either v4 or v6, to identify end points and intermediate switches and routers. This makes MPLS networks IP-compatible and easily integrated with traditional IP networks. However, unlike traditional IP, MPLS flows are connection-oriented and packets are routed along pre-configured Label Switched Paths (LSPs).

MPLS – What is ?

Short for Multiprotocol Label Switching, an IETF initiative that integrates Layer 2 information about network links (bandwidth, latency, utilization) into Layer 3 (IP) within a particular autonomous system–or ISP–in order to simplify and improve IP-packet exchange. MPLS gives network operators a great deal of flexibility to divert and route traffic around link failures, congestion, and bottlenecks.

How To Find Your IP and MAC Addresses On Windows XP | 2000 | NT

Follow these steps to quickly find the Internet Protocol (IP) and Media Access Control (MAC) address of a computer running Windows XP, Windows 2000, or Windows NT.

Difficulty: Easy

Time Required: seconds

Here’s How:

1. Click the Start menu button on the Windows taskbar.
2. Click Run… on this menu.
3. Type cmd in the text box that appears. A command prompt window launches on the desktop.
4. In this command window, type ipconfig /all. Details are shown for each of the computer’s network adapters. Computers installed with VPN software or emulation software will possess one or more virtual adapters. <!–more–>
5. The IP Address field states the current IP address for that network adapter.
6. The Physical Address field states the MAC address for that adapter.

Tips:

1. Take care to read the IP address from the correct adapter. Virtual adapters generally show a private address rather than an actual Internet address.
2. Virtual adapters possess software-emulated MAC addresses and not the actual physical address of the network interface card.

What You Need:

• Windows XP / 2000 / NT

From Bradley Mitchell,
Your Guide to Wireless / Networking.

MTU – What is ?

Definition: The MTU is a limit, expressed in bytes, on the size of data sent over a network. It is the maximum size of a single unit (e.g., an Ethernet frame) of digital communications.

MTU sizes are properties of physical network interfaces. The MTU for Ethernet, for instance, is 1500 bytes. Some types of networks (like Token Ring) have larger MTUs, and some types have smaller MTUs. Higher-level network protocols like TCP/IP can be configured with a maximum packet size, but this setting is distinct from the physical MTU. The MTU of a network has important implications on the performance of computer communications as explained below.

In Microsoft Windows, the maximum packet size for protocols like TCP can be set in the Registry. If this value is set too low, streams of network traffic will be broken up into a relatively large number of small packets that adversely affects performance. If the maximum TCP packet size is set too high, it will exceed the network’s MTU and also degrade performance by requiring that each packet be subdivided into at least two smaller ones (a process known as fragmentation).

Multihoming – What is ?

Definition: Multihoming is the configuration of multiple network interfaces or IP addresses on a single computer. Multihoming is intended to increase the reliability of network applications but it does not necessarily improve their performance.In traditional multihoming, you install a second hardware network adapter on a computer that normally possesses only one. Then, you configure both adapters to utilize the same one local IP address. This setup allows a computer to continue using the network even if one or the other network adapter stops functioning. You can also connect these adapters to different Internet/network access points and increase the total bandwidth available to use across multiple applications.

An alternate form of multihoming does not require a second network adapter; instead, you assign multiple IP addresses to the same adapter on one computer.

Microsoft Windows and other operating systems support this configuration as an advanced IP addressing option. This approach gives you more flexibility to control incoming network connections from other computers.

Guide To ARP, IARP, RARP, and Proxy ARP

When I first started studying for my CCNA years ago, one of the (many) things that confused me was ARP. Or rather, what ARP did as opposed to Reverse ARP, Inverse ARP, and Proxy ARP! One book would mention ARP without mentioning the other variations, one would mention RARP but not Proxy ARP, and so on…

I got through my Intro and ICND exams, but I never forgot how confusing this was to me when I started. (And we all start somewhere!) To help current CCNA candidates with this confusing topic, let’s take a look at each one of these technologies.

ARP – Address Resolution Protocol
You may well know what ARP does from your networking studies or work on a LAN, but to effectively troubleshoot ARP issues on a WAN (and pass the 640-801, 640-811, and 640-821 exams!), you need to take network devices into account that may be separating the workstations in question.

BackTrack – Comprehensive Security Penetration Linux Distro Suite

The are a couple of things that are essential to any hacker’s walk of life. To name a few, there’s the ubiquitous flash drive for data transfer. You have the crossover cable for even faster data transfer. There’s the WiFi antenna for high gain and strong amplification. Possibly, you might find a video capture card in the computer. Of course, there’s the ubiquitous laptop and desktop computer. But what software is on these computers? Undoubtedly, you will find at least two operating systems, most often Windows and Linux. But with Linux, there are several different distributions. Is there a specific one? With hackers and crackers, there is only one Linux distro out there. It is called Backtrack.