CEH: Certified Ethical Hacker: The Phases of Ethical Hacking

The Phases of Ethical Hacking

The process of ethical hacking can be broken down into five distinct phases.

An ethical hacker follows processes similar to those of a malicious hacker. The steps to gain and maintain entry into a computer system are similar no matter what the hacker's intentions are. Figure 1 illustrates the five phases that hackers generally follow in hacking a computer system.

Figure 1: Phases of hacking

Phase 1: Passive and Active Reconnaissance

Passive reconnaissance involves gathering information about a potential target without the targeted individual's or company's knowledge. Passive reconnaissance can be as simple as watching a building to identify what time employees enter the building and when they leave. However, most reconnaissance is done sitting in front of a computer.

When hackers are looking for information on a potential target, they commonly run an Internet search on an individual or company to gain information. I'm sure many of you have performed the same search on your own name or a potential employer, or just to gather information on a topic. This process when used to gather information regarding a TOE is generally called information gathering. Social engineering and dumpster diving are also considered passive information-gathering methods.

Sniffing the network is another means of passive reconnaissance and can yield useful information such as IP address ranges, naming conventions, hidden servers or networks, and other available services on the system or network. Sniffing network traffic is similar to building monitoring: a hacker watches the flow of data to see what time certain transactions take place and where the traffic is going. Sniffing network traffic is a common hook for many ethical hackers. Once they use some of the hacking tools and are able to see all the data that is transmitted in the clear over the communication networks, they are eager to learn and see more.

Sniffing tools are simple and easy to use and yield a great deal of valuable information which literally let you see all the data that is transmitted on the network. Many times this includes usernames and passwords and other sensitive data. This is usually quite an eye-opening experience for many network administrators and security professionals and leads to serious security concerns.

Active reconnaissance involves probing the network to discover individual hosts, IP addresses, and services on the network. This process involves more risk of detection than passive reconnaissance and is sometimes called rattling the doorknobs. Active reconnaissance can give a hacker an indication of security measures in place (is the front door locked?), but the process also increases the chance of being caught or at least raising suspicion. Many software tools that perform active reconnaissance can be traced back to the computer that is running the tools, thus increasing the chance of detection for the hacker.

Both passive and active reconnaissance can lead to the discovery of useful information to use in an attack. For example, it's usually easy to find the type of web server and the operating system (OS) version number that a company is using. This information may enable a hacker to find a vulnerability in that OS version and exploit the vulnerability to gain more access.

Phase 2: Scanning

Scanning involves taking the information discovered during reconnaissance and using it to examine the network. Tools that a hacker may employ during the scanning phase include

Dialers
Port scanners
Internet Control Message Protocol (ICMP) scanners
Ping sweeps
Network mappers
Simple Network Management Protocol (SNMP) sweepers
Vulnerability scanners

Hackers are seeking any information that can help them perpetrate an attack on a target, such as the following:

Computer names
Operating system (OS)
Installed software
IP addresses
User accounts

Phase 3: Gaining Access

Phase 3 is when the real hacking takes place. Vulnerabilities exposed during the reconnaissance and scanning phase are now exploited to gain access to the target system. The hacking attack can be delivered to the target system via a local area network (LAN), either wired or wireless; local access to a PC; the Internet; or offline. Examples include stack-based buffer overflows, denial of service, and session hijacking. Gaining access is known in the hacker world as owning the system because once a system has been hacked, the hacker has control and can use that system as they wish.

Phase 4: Maintaining Access

Once a hacker has gained access to a target system, they want to keep that access for future exploitation and attacks. Sometimes, hackers harden the system from other hackers or security personnel by securing their exclusive access with backdoors, rootkits, and Trojans. Once the hacker owns the system, they can use it as a base to launch additional attacks. In this case, the owned system is sometimes referred to as a zombie system.

Phase 5: Covering Tracks

Once hackers have been able to gain and maintain access, they cover their tracks to avoid detection by security personnel, to continue to use the owned system, to remove evidence of hacking, or to avoid legal action. Hackers try to remove all traces of the attack, such as log files or intrusion detection system (IDS) alarms. Examples of activities during this phase of the attack include