Types of Attacks on a System

These are the Passive type of Computer Attacks:

Eavesdropping:

 This is the process of listening in or overhearing parts of a conversation. It also includes attackers listening in on your network traffic. Its generally a passive attack, for example, a coworker may overhear your dinner plans because your speaker phone is set too loud. The opportunity to overhear a conversation is coupled with the carelessness of the parties in the conversation.

Identity spoofing:

Every computer has an IP address, due to which it is considered as a valid and independent entity on the network. One of the common computer attacks is to assume the identity of another computer. Here IP packets may be sent from valid addresses and gain access to a particular IP.once access is gained, the data on the system may be deleted, modified or rerouted .Alternatively, the hacker can make use of this hacked IP and cause attacks on the other systems within or outside the network.

Snooping Attacks:

This is when someone looks through your files in the hopes of finding something interesting whether it is electronic or on paper. In the case of physical snooping people might inspect your dumpster, recycling bins, or even your file cabinets; they can look under your keyboard for post-It-notes, or look for scraps of paper tracked to your bulletin board. Computer snooping on the other hand involves someone searching through your electronic files trying to find something interesting.

Interception:

This can be either an active or passive process. In a networked environment, a passive interception might involve someone who routinely monitors network traffic. Active interception might include putting a computer system between sender and receiver to capture information as it is sent. From the perspective of interception, this process is covert. The last thing a person on an intercept mission wants is to be discovered. Intercept missions can occur for years without the knowledge of the intercept parties.

Replay Attacks:  (Replay an authentication session to fool a computer into granting access)

These are becoming quite common, this occur when information is captured over a network. Replay attacks are used for access or modification attacks. In a distributed environment, logon and password information is sent over the network between the client and the authentication system. The attacker can capture this information and replay it later. This can also occur security certificates from systems such as Kerberos: The attacker resubmits the certificate, hoping to be validated by the authentication system, and circumvent any time sensitivity.

Data Modification Attacks:

This involves the deletion, insertion, or alteration of information in an unauthorized manner that is intended to appear genuine to the user. These attacks can be very hard to detect. The motivation of this type of attack may be to plant information, change grades in a class, alter credit card records, or something similar. Website defacements are a common form of modification attacks.

Repudiation Attacks:

This makes data or information to appear to be invalid or misleading (Which can even be worse). For example, someone might access your email server and inflammatory information to others under the guise of one of your top managers. This information might prove embarrassing to your company and possibly do irreparable harm. This type of attack is fairly easy to accomplish because most email systems don't check outbound email for validity. Repudiation attacks like modification attacks usually begin as access attacks.

Dos Attacks:

Denial of service (DoS) forces the target computer to allocate so much memory for TCP connections so that it runs out of memory.

1.     Ping of death - Uses IP to cause large packets to be reassembled in order to make the target computer crash.

2.     A common DoS attack is to open as many TCP sessions as possible; This type of attack is called TCP SYN flood DoS attack.

DDos Attacks:

Distributed Denial-of-services this is similar to a DoS attack. This type of attack amplifies the concepts of DoS attacks by using multiple computer systems to conduct the attack against a single organization. These attacks exploit the inherent weaknesses of dedicated networks such as DSL and Cable. The conclusion is that uses many machines to attack one system or network.

Password Guessing Attacks:

This occurs when an account is attacked repeatedly. This is accomplished by sending possible passwords to an account in a systematic manner. These attacks are initially carried out to gain passwords for an access or modification attack. There are two types of password guessing attacks:

Brute-force attack: Attempt to guess a password until a successful guess occurs. This occurs over a long period. To make passwords more difficult to guess, they should be longer than two or three characters (Six should be the bare minimum), be complex and have password lockout policies.
Dictionary attack: This uses a dictionary of common words to attempt to find the users password. Dictionary attacks can be automated, and several tools exist in the public domain to execute them.

Man-in-the-Middle Attacks:

During this attack an attacker can read, insert and modify any messages between two other people or computers without either victim knowing that the connection between them has been compromised. The attacker can observe and intercept messages going between the two victims. The attacker can change the message content going to both victims.

Back door Attacks:

Also called a trapdoor this can have two different meanings, the original term back door referred to troubleshooting and developer hooks into systems. During the development of a complicated operating system or application, programmers add back doors or maintenance hooks. These back doors allow them to examine operations inside the code while the program is running.

The second type of back door refers to gaining access to a network and inserting a program or utility that creates an entrance for an attacker. The program may allow a certain user to log in without a password or gain administrative privileges. A number of tools exist to create a back door attack such as, Back Orifice (Which has been updated to work with windows server 2003 as well as earlier versions), Subseven, NetBus, and Net Devil. There are many more. Fortunately, most anti-virus software will recognize these attacks.

Spoofing Attacks:

A spoofing attack is when a malicious party impersonates another device or user on a network in order to launch attacks against networks hosts, steal data, spread malware, or bypass access controls. There are several different types of spoofing attacks that malicious parties can use to accomplish this. Some of the most common methods include IP address spoofing attacks, ARP (Address resolution Protocols) spoofing attacks and DNS server spoofing attacks.

Compromised-Key Attacks:

To store sensitive data, a secret code or number may be used. Obtaining the key is no doubt a real huge task for the hacker; it is possible that after intense research the hacker is indeed able to lay his hands on the key. Once the key is in possession of the hacker will now have access to the sensitive data and can make change to the data.However, there are also chances that the hacker will try different permutations and combination of the key to gain access to other sets of sensitive data as well.

Application-Layer Attacks:

The aim of the application layer attack is to cause fault in the server’s operating system once a fault is created in the operating system, the hacker is able to gain access to the server controls. This in turn leads to the hacker modifying the data in various ways. A virus may be introduced into the system or may send numerous requests to the server, which can result in its crash or security controls may be disabled, due to which restoring the server back can became difficult.