GeekPhilosopher:Security- hackers/crackers use trojan horses, packet sniffers, denial of service

What's soooooo important inside that network?

Unauthorized access is age old. It began with the Romans and their poor, landless citizens attempting to infiltrate

colossal Roman castles. The concept within Internet hacking is relatively similar, all based around a single theme: information. Those with information, therefore, have access and power, even if it is confined to one particular network, for a short amount of time. The importance, then, of hacking, can be said to include information and power. Gravy...

This begs the question of how these hackers gain access to networks. Some common tricks include password deciphering, buffer overflows, scripts and DoS attacks. The purpose of this article is to introduce you to what exactly hackers do to gain access, and to quench the steadfast intrigue of these concepts.

What are hackers? What are crackers?

Definitions for these two terms vary, but suffice it to say that hackers are those exceptionally knowledgeable computer users, often skilled in programming languages and Internet logic. The term hacker, then, can conceivably be used with either a positive or negative connotation. Throughout the years, this term has gained much momentum to the negative. Now, the term often means to gain access to a network, after hacking their way in.

The term crack means to break into a computer system. Hackers wish to differentiate the two terms, as hackers are said to strive towards information for the purposes of pranks, or web site 'modification'. Crackers, on the other hand, have a specific purpose to break into secure systems, capture the password(s) and wreak havoc on the machine.

Since these two terms are often used reciprocally, this article will exercise the terms hacker and hack, opposed to cracker and crack.

Efforts to gain passwords

SIMPLE INVESTIGATION

Let's get into the meat and potatoes of what hacking is all about: capturing the often illusive password. By their nature, passwords should be illusive, but hackers contrive methods and techniques to gather them, and use them for their own purposes within a network. The password is the lowest, but ultimately the most important, step in the hacking totem pole. Once a password is compromised (or seized), hackers use it to realize additional rights and privileges within the system.

So, how are passwords seized? Regardless of how secure the network itself is, there are always insecurities, and that includes the actual users of the network (or, Mr. Do Mas). Sure, hackers can use sophisticated password utilities to guess passwords on a system, but oftentimes a little investigation provides what the hacker is looking for.

Believe it or not, a major source of password compromise is the simple laziness of users. Users write the passwords down on little Post-It notes and place them within their desk. Users give their passwords to others. Passwords are printed out on pieces of paper that are often thrown out whole. A little rummaging through an office and its waste can surface more information than you might imagine.

Hackers also use a technique known as social engineering. They may call up a network administrator, pose as a confused network user and claim that they lost his or her password. This works way too often and many times is the first thing that hackers try.

TROJAN HORSES

The war between the Achaeans and the Trojans continued for 10 long years. After the death of Achilles (known as the greatest warrior among the Greeks), the Achaeans constructed a wooden horse and filled it with warriors and brought it into the city of Troy. Once inside, the warriors exploded from the wooden horse and destroyed the city; or so the legend goes.

A trojan horse in computer terms means essentially the same thing, a seemingly harmless computer program infiltrates the computer system, while malicious routines are being executed behind the scenes. One of the first trojan horses was a program that impersonated a login box. Once the user enters his or her password, they are saved in a location that the hacker has access to. This type of trojan horse is commonly installed on library computers, or an otherwise public computing environment.

Trojan horses are often more disguised than a simple login prompt. Windows and Linux system commands, for example, are susceptible to manipulation. Without getting into technicalities, the windows command edit can be compromised and instructed to launch a malignant batch file behind the scenes, deleting or even adding user accounts with administrator privileges.

Remember that a trojan horse is an executable file, which can be recognized with the .exe, .vbs, .com, etc extensions. A trojan horse sent through e-mail can often be found by noticing an extension like .txt.vbs.

PACKET SNIFFERS

Network data travels through network media in variable sized packets. These packets, of course, are never seen in their raw form, as a series of network protocol rules convert such packets to data that applications can interpret and display. However, before data packet arrives at the recipient's computer, the packet can be snatched out of the media by packet sniffing software.

Because such utilities, like Telnet or SNMP, were designed to send passwords over network media in plaintext, or unencrypted form, passwords can be easily compromised using this method. Note that packet sniffers are capturing utilities, and cannot be used to actually modify any of the seized data packets. Sniffers can capture data within multiple protocols, like IP (Internet Protocol), UDP (User Datagram Protocol) and TCP (Transmission Control Protocol), allowing a single application to function well within a wide array of computing environments.

Passwords are not the only way hackers gain access to networks. Next, we will take a look at buffer overflows, and what it provides to hackers.

Buffer overflow

When data is sent over networks, the receiving computer must allocate enough memory to handle the incoming data packets. The space that incoming packets are stored in is called the buffer. If the operating system does a poor job of managing the buffer, or if the buffer overflows, problems occur. Because applications now check the size of the receiving data before placed within the buffer, poorly designed applications often fall prey to this type of attack.

The Unix program Sendmail, used on the Internet for sending mail from a form to an e-mail address, has a widely known vulnerability to buffer overflows and is often attacked. If packets are sent to the destination at a high rate of speed, the computer or program can be rendered useless. This leads us to DoS attacks, which is extremely similar to the logic behind buffer overflows.

DoS (Denial of Service) attacks

Lately, Denial of Service attacks have become a popular method to overflow the destination computer system with packets of information. The purpose of a DoS attack is to utilize as many system resources as possible, disabling the system from performing any other task. This, essentially, is denying service to legitimate users.

DoS attacks are usually performed from a very high-speed network to a network of the same speed, or slower. If the initiating network, or the network the hacker is on, is fast enough, the hacker can instruct his or her computer to flood the destination network with packets of information. This type of attack, however, gets especially hairy when we talk about distributed DoS attacks.

A distributed attack, as you might have guessed, consists of more than one initiating network and, therefore, more than one hacker working together. A group of hackers will, at the same time and from different, high-speed networks, flood the destination system with data packets. In extreme circumstances, thousands of hackers on thousands of networks can send data to a single machine, clearly rendering it useless. These types of attacks are almost impossible to stop after it starts, as eBay and Yahoo found out a couple years ago.

One way to gain access to more computers and, therefore, more data packets, is to send a ping request to all computers on a network. A ping is simply an electronic pulse whose sole purpose is to detect the presense of a machine by IP address. Once the destination machine receives the ping, it sends a response back to the originating system that sent the ping. That said, the hacker simply forges the initiation computer's address to the victim's IP address, sends pings out to large networks, and each computer system will send a response back to the victim's system instead of the actual sending (the hacker's) machine. This is known as a smurf attack.

Let's wrap it up

This article examined what hackers are, why they hack and how they hack. Hacks can be as informal as a little investigation around the office to a sophisticated trojan horse program, disguised as a useful application. Hackers often do a little packet sniffing on networks in an attempt to grab passwords and other sensitive information from traveling across the network media. We then took a stab at buffer overflows, what they are and, lastly, the popular DoS attack. When performed correctly, hackers can utilize these effective techniques to both disrupt network traffic and also gain entry to restricted systems.