Checking Malware Name

Created the Tuesday 22 September 2020. Updated 6 months, 2 weeks ago.

Malware can use various techniques to evade detection by security analysts and researchers. One such technique is to check the name of the malware sample before fully executing on the infected machine. If the sample has been renamed to a blacklisted name, such as "malware.exe" or "sample.exe", or even with the file hash, the malware can detect this and change its behavior or terminate its process to avoid being detected and analyzed. This technique allows the malware to remain undetected and continue its malicious activities on the infected machine.

Technique Identifiers

U1303 U0401

Technique Tags

malware sample blacklisted names process file hash

Code Snippets

#include <iostream>
#include <cstring>
#include <windows.h>

using namespace std;

int main(int argc, char** argv)
{
    TCHAR szExeFileName[MAX_PATH];
    GetModuleFileName(NULL, szExeFileName, MAX_PATH);

    // full path
    cout << "[+] Full Path: " << szExeFileName << endl;

    //convert tchar to string
    std:string filename (szExeFileName);

    // Remove directory if present.
    const size_t last_slash_idx = filename.find_last_of("\\/");
    if (std::string::npos != last_slash_idx)
    {
        filename.erase(0, last_slash_idx + 1);
    }

    // Blacklist
    LPSTR fname[] = {"sample.exe",
                     "malware.exe",
                     // ADD YOUR PROCESS NAME HERE!
                    };
    for (int i = 0; i < (sizeof(fname) / sizeof(LPSTR)); i++)
    {
        if ((fname[i] == filename ))
        {
            cout << " [!] Filename is blacklisted: " << (fname[i]) << endl;
            exit(0);
        }
    }
    return 0;
}

Detection Rules

                                    rule MalwareNameEvasion
{
    strings:
        // Check for the GetModuleFileName() function call
        $get_module_filename = "GetModuleFileName"

        // Check for the find_last_of() method call
        $find_last_of = "find_last_of"

        // Check for the std::string data type
        $string = "std::string"

        // Check for the "\\/" string
        $backslash_slash = "\\\\/"

        // Check for the "sample.exe" string
        $sample_exe = "sample.exe"

        // Check for the "malware.exe" string
        $malware_exe = "malware.exe"

    condition:
        // Check if all the required strings are present in the code
        all of them
}