Bad String Format

Created the Monday 18 March 2019. Updated 9 months, 4 weeks ago.

Bad string format is a technique used by malware to evade detection and analysis by OllyDbg, a popular debugger used by security researchers and analysts. This technique involves using malformed strings that exploit a known bug in OllyDbg, causing the debugger to crash or behave unexpectedly.

For example, the malware may use a string with multiple %s inputs, which OllyDbg is not able to handle correctly. This causes the debugger to crash or behave in an unpredictable manner, making it difficult for the analyst to continue their analysis. This technique can be effective in disrupting the analysis process and making it more difficult for the analyst to understand the malware's capabilities and behavior. However, it is only effective against OllyDbg, and other debuggers may not be affected by this technique.

Featured Windows API's

Below, you will find a list of the most commonly used Windows API's that are currently utilized by malware authors for current evasion technique. This list is meant to provide an overview of the API's that are commonly used for this purpose. If there are any API's that you feel should be included on this list, please do not hesitate to contact us. We will be happy to update the list and provide any additional information or documentation that may be helpful.

Code Snippets

Detection Rules

Additional Resources

External Links

The resources provided below are associated links that will give you even more detailed information and research on current evasion technique. It is important to note that, while these resources may be helpful, it is important to exercise caution when following external links. As always, be careful when clicking on links from unknown sources, as they may lead to malicious content.

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