Microsoft Risk Intelligence in December noticed a “menace actor” utilizing a publicly accessible ASP.NET machine key to inject malicious code and fetch the Godzilla post-exploitation framework, a “backdoor” net shell utilized by intruders to execute instructions and manipulate information. The corporate then recognized greater than 3,000 publicly disclosed ASP.NET machine keys—i.e., keys that had been disclosed in code documentation and repositories—that may very well be utilized in these kinds of assaults, referred to as ViewState code injection assaults.
In response, Microsoft Risk 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 Risk Intelligence stated that in investigating and defending towards 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 had been then utilized by menace actors to carry out malicious actions on course servers. Whereas many beforehand recognized ViewState code injection assaults used compromised or stolen keys that had been offered on darkish net boards, these publicly disclosed keys might pose a better threat as a result of they’re accessible in a number of code repositories and will have been pushed into improvement code with out modification, Microsoft stated. The restricted malicious exercise Microsoft noticed in December included using one publicly disclosed key to inject malicious code. Microsoft Risk Intelligence continues to watch the extra use of this assault method, Microsoft stated.
ViewState is the tactic by which ASP.NET net types protect web page and management between postbacks, Microsoft Risk Intelligence stated. Knowledge for ViewState is saved in a hidden area on the web page and is encoded. To guard ViewState towards tampering and disclosure, the ASP.NET web page framework makes use of machine keys. “If these keys are stolen or made accessible to menace actors, these menace actors can craft a malicious ViewState utilizing the stolen keys and ship it to the web site by way of a POST request,” Microsoft Risk 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 fitting keys are used. The malicious code is then loaded into the employee course of reminiscence and executed, offering the menace actor distant code execution capabilities on the goal IIS net server.”
