Microsoft Menace Intelligence in December noticed a “risk actor” utilizing a publicly accessible ASP.NET machine key to inject malicious code and fetch the Godzilla post-exploitation framework, a “backdoor” internet shell utilized by intruders to execute instructions and manipulate recordsdata. The corporate then recognized greater than 3,000 publicly disclosed ASP.NET machine keys—i.e., keys that have been disclosed in code documentation and repositories—that may very well be utilized in most of these assaults, referred to as ViewState code injection assaults.
In response, Microsoft Menace Intelligence is warning organizations to not copy keys from publicly accessible sources and urging them to repeatedly rotate keys. In a February 6 bulletin, Microsoft Menace Intelligence stated that in investigating and defending in opposition to this exercise, it has noticed an insecure observe whereby builders used publicly disclosed ASP.NET machine keys from code documentation, repositories, and different public sources that have been then utilized by risk actors to carry out malicious actions on course servers. Whereas many beforehand recognized ViewState code injection assaults used compromised or stolen keys that have been offered on darkish internet boards, these publicly disclosed keys may pose a better danger as a result of they’re accessible in a number of code repositories and will have been pushed into growth code with out modification, Microsoft stated. The restricted malicious exercise Microsoft noticed in December included the usage of one publicly disclosed key to inject malicious code. Microsoft Menace Intelligence continues to observe the extra use of this assault approach, Microsoft stated.
ViewState is the tactic by which ASP.NET internet types protect web page and management between postbacks, Microsoft Menace Intelligence stated. Information for ViewState is saved in a hidden area on the web page and is encoded. To guard ViewState in opposition to tampering and disclosure, the ASP.NET web page framework makes use of machine keys. “If these keys are stolen or made accessible to risk actors, these risk actors can craft a malicious ViewState utilizing the stolen keys and ship it to the web site through a POST request,” Microsoft Menace Intelligence stated within the bulletin. “When the request is processed by ASP.NET Runtime on the focused server, the ViewState is decrypted and validated efficiently as a result of the proper keys are used. The malicious code is then loaded into the employee course of reminiscence and executed, offering the risk actor distant code execution capabilities on the goal IIS internet server.”
