| 1.2 |  | Vulnerabilities and Threats |
| 1.2.5 |  | Access |

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

Some examples of methods used by hackers include the following:

- Exploit easily guessed passwords .

- Brute force
- Cracking tools
- Dictionary attacks

- Exploit misconfigured services

- IP services such as anonymous FTP, TFTP, and remote registry access
- Trust relationships through spoofing and r-services
- File sharing services such as NFS and Windows File Sharing

- Exploit application holes

- Mishandled input data

- Access outside application domain, buffer overflows, race conditions

- Protocol weaknesses

- Fragmentation, TCP session hijack
- Trojan horses

- Programs that introduce an inconspicuous backdoor into a host

- Social engineering

- posing as a network administrator to gain information from users
- look for written usernames and passwords near computer or server terminals
- Dumpster diving searching through trash cans to find access information

Unauthorized data retrieval is simply reading, writing, copying, or moving files that are not intended to be accessible to the intruder. Sometimes this is as easy as finding shared folders in Windows, Unix, or Macintosh file systems that have read or read and write access set for everyone.

Man-in-the-middle attack
A man-in-the-middle attack requires that the hacker have access to network packets that come across a network. An example could be someone who is working for an Internet service provider (ISP) and has access to all network packets transferred between the ISP network and any other network.

Such attacks are often implemented using network packet sniffers and routing and transport protocols. The possible uses of such attacks are theft of information, hijacking of an ongoing session to gain access to private network resources, traffic analysis to derive information about a network and its users, Denial of Service (DoS), corruption of transmitted data, and introduction of new information into network sessions.

Trust exploitation
Although it is more of a technique than a hack itself, trust exploitation refers to an attack in which an individual takes advantage of a trust relationship within a network . The classic example is a perimeter network connection from a corporation. These network segments often house Domain Name System (DNS), Simple Mail Transfer Protocol (SMTP), and Hypertext Transfer Protocol (HTTP) servers. Because all these servers reside on the same segment, the compromise of one system can lead to the compromise of other systems because these systems usually trust other systems attached to the same network.

Another example is a system on the outside of a firewall that has a trust relationship with a system on the inside of a firewall. When the outside system is compromised, it can take advantage of that trust relationship to attack the inside network. Another form of an access attack involves privilege escalation. Privilege escalation occurs when a user obtains privileges or rights to objects that were not assigned to the user by an administrator. Objects can be files, commands, or other components on a network device. The intent is to gain access to information or execute unauthorized procedures. This information will be used to gain administrative privileges to a system or device. They use these privileges to install sniffers, create backdoor accounts, or delete log files.