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Microsoft IIS Unicode Exploits

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Unicode is a superset of the Latin, Greek, and other character sets that were previously used on the Internet. Unicode includes more characters than the other character sets, but it also includes unique characters not found in the other character sets. Unicode also includes punctuation, mathematical and text-processing symbols, and identifiers all of which make it a versatile and powerful set of characters. Because Unicode is so useful, hackers use it to perform dangerous cyber attacks.

IIS Unicode Exploit:

IIS Unicode exploits are a type of vulnerability found in Microsoft web servers that allows for the execution of arbitrary code. This post will look at what it is, how it works, and how to protect your system from these types of vulnerabilities. IIS Unicode exploits are a type of vulnerability found in Microsoft web servers (Internet Information Services) that allows for executing arbitrary code. They take advantage of an encoding scheme vulnerability within IIS and can allow an attacker to execute malicious scripts on the victim’s machine without them knowing.

The vulnerability itself is due to a combination of factors. The first is the way IIS allows HTTP requests to be encoded. Secondly, how IIS 5.0, 6.0, and 7.0, handle very long strings in the particular website make this type of attack possible. Lastly, some websites are vulnerable because they are hosted on IIS platforms that permit this attack (e.g., MSN). The severity of the problem with these types of vulnerabilities can be seen in that there is an official patch released by Microsoft to protect against them, at least from IIS 7.0 and above.

Unicode Exploit:

One of the most common uses for an ethical hacker is to breach computer systems protected by Unicode encryption. Unicode exploits a vulnerability in computers that use the East Asian character set-which Unicode represents by a picture of a peach (the symbol for Chinese). Unicode contains over 80,000 characters, including full letters, numerals, punctuation, and symbols used in writing systems from around the world. Exploiting a weakness in this format is easy because there are so many possibilities- especially when used by hackers. Unicode characters can be used as codes that bypass security measures, open ports to allow other codes to pass through, delete files, or even spread malware throughout a system. A Unicode exploit is a security vulnerability that takes advantage of how Microsoft’s IIS web server processes Unicode characters to execute malicious code on the victim’s system. Specifically, this vulnerability (in IIS 5.0 and 6.0) allows for the remote execution of programs. This means that a remote attacker can cause a program to be run and thus execute arbitrary code remotely on the victim’s machine under their user account (i.e., login credentials).

Working of IIS Unicode Exploit:

  • The hack is based on how IIS handles requests that contain very long character strings.
  • The way that IIS handles requests that contain very long character strings varies from one version of the server to another. For those versions that are affected by this vulnerability, the request can cause a buffer overflow. 
  • This type of attack is well known in the security community due to how common it is and how severe the impact can be on a victim’s system.
  • For this exploit to work, an attacker must be able to send overly long strings of Unicode characters (i.e., beyond what IIS will accept) in an HTTP request for their web server to process. 
  • This causes the server to buffer more data than it can handle and therefore a buffer overflow. This in turn can allow for remote code execution over the internet.
  • IIS versions before 7.0 were vulnerable, but as IIS 7.0 and above offer protection against these types of vulnerabilities, webmasters should update their servers to these versions of the web server as soon as reasonably practical.
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Last Updated : 18 Oct, 2022
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