Scanning Anonymously

Preparing proxy servers is the last step in the CEH scanning methodology. A proxy server is a computer that acts as an intermediary between the hacker and the target computer.

Using a proxy server can allow a hacker to become anonymous on the network. The hacker first makes a connection to the proxy server and then requests a connection to the target computer via the existing connection to the proxy. Essentially, the proxy requests access to the target computer, not the hacker's computer. This lets a hacker surf the Web anonymously or otherwise hide their attack.

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Hacking Tools

SocksChain is a tool that gives a hacker the ability to attack through a chain of proxy servers. The main purpose of doing this is to hide the hacker's real IP address and therefore minimize the chance of detection. When a hacker works through several proxy servers in series, it's much harder to locate the hacker. Tracking the attacker's IP address through the logs of several proxy servers is complex and tedious work. If one of the proxy servers' log files is lost or incomplete, the chain is broken, and the hacker's IP address remains anonymous.

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Anonymizers are services that attempt to make web surfing anonymous by utilizing a website that acts as a proxy server for the web client. The first anonymizer software tool was developed by Anonymizer.com; it was created in 1997 by Lance Cottrell. The anonymizer removes all the identifying information from a user's computers while the user surfs the Internet, thereby ensuring the privacy of the user.

To visit a website anonymously, the hacker enters the website address into the anonymizer software, and the anonymizer software makes the request to the selected site. All requests and web pages are relayed through the anonymizer site, making it difficult to track the actual requester of the web page. Use Anonymouse to web surf anonymously in Exercise 1.

Exercise 1: Use Anonymouse to Surf Websites Anonymously

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1. Open a web browser to the http://anonymouse.org website and select English at the top of the page.
2. Type a website address in the Enter Website Address field and click the Surf Anonymously button.
   This works especially well if you know certain websites are blocked.

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A popular method of bypassing a firewall or IDS is to tunnel a blocked protocol (such as SMTP) through an allowed protocol (such as HTTP). Almost all IDS and firewalls act as a proxy between a client's PC and the Internet and pass only the traffic defined as being allowed.

Most companies allow HTTP traffic because it's usually benign web access. However, a hacker using an HTTP tunneling tool can subvert the proxy by hiding potentially destructive protocols, such as IM or chat, within an innocent-looking protocol packet.

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Hacking Tools

HTTPort, Tunneld, and BackStealth are tools to tunnel traffic through HTTP. They allow the bypassing of an HTTP proxy, which blocks certain protocols from accessing the Internet. These tools allow the following potentially dangerous software protocols to be used from behind an HTTP proxy:

• Email
• IRC
• ICQ
• News
• AIM
• FTP

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A hacker can spoof an IP address when scanning target systems to minimize the chance of detection. One drawback of spoofing an IP address is that a TCP session can't be successfully completed.

Source routing lets an attacker specify the route that a packet takes through the Internet. This can also minimize the chance of detection by bypassing IDS and firewalls that may block or detect the attack. Source routing uses a reply address in the IP header to return the packet to a spoofed address instead of the attacker's real address. 

To detect IP address spoofing, you can compare the time to live (TTL) values: the attacker's TTL will be different from the spoofed address's real TTL.