Types of Network Attacks

There are four primary classes of attacks.

Reconnaissance

Reconnaissance is the unauthorized discovery and mapping of systems, services, or vulnerabilities. It is also known as information gathering and, in most cases, it precedes another type of attack. Reconnaissance is similar to a thief casing a neighborhood for vulnerable homes to break into, such as an unoccupied residence, easy-to-open doors, or open windows.
Reconnaissance attacks can consist of the following:

-Internet information queries
-Ping sweeps
-Port scans
-Packet sniffers

Access

System access is the ability for an intruder to gain access to a device for which the intruder does not have an account or a password. Entering or accessing systems usually involves running a hack, script, or tool that exploits a known vulnerability of the system or application being attacked.
Access attacks can consist of the following:

-Password Attacks
-Trust Exploitation
-Port Redirection
-Man-in-the-Middle Attack

Denial of Service(DoS)

Denial of service is when an attacker disables or corrupts networks, systems, or services with the intent to deny services to intended users. DoS attacks involve either crashing the system or slowing it down to the point that it is unusable. But DoS can also be as simple as deleting or corrupting information. In most cases, performing the attack involves simply running a hack or script. For these reasons, DoS attacks are the most feared.
The following are some examples of common DoS threats:

-Ping of Death
-SYN Flood
-DDos Attacks
-Smurf Attack

Worms, Viruses, and Trojan Horses

Malicious software can be inserted onto a host to damage or corrupt a system, replicate itself, or deny access to networks, systems, or services. Common names for this type of software are worms, viruses, and Trojan horses.
The anatomy of a worm attack is as follows:

-The enabling vulnerability-A worm installs itself by exploiting known vulnerabilities in systems, such as naive end users who open unverified executable attachments in e-mails.
-Propagation mechanism-After gaining access to a host, a worm copies itself to that host and then selects new targets.
-Payload-Once a host is infected with a worm, the attacker has access to the host, often as a privileged user. Attackers could use a local exploit to escalate their privilege level to administrator.