Modern malware like CryptoLocker frequently leverages standard Windows directories for execution because:

• These locations have write permissions by default (no admin rights required)
• Path randomization makes detection harder (%appdata% resolves differently per user)
• Temporary folders naturally avoid scrutiny from users and some security tools

// Example malware persistence technique using %appdata%
string payloadPath = Environment.ExpandEnvironmentVariables(
    "%appdata%\\Microsoft\\Windows\\Start Menu\\Programs\\Startup\\malware.exe");
File.Copy(currentProcessPath, payloadPath);

Common technical approaches to enforce these restrictions:

Via Group Policy (GPO):

Computer Configuration → Policies → Windows Settings
→ Security Settings → Software Restriction Policies
→ Additional Rules → New Path Rule

Using PowerShell automation:

# Block execution from Temp directories
$ruleAction = "Deny"
$tempPaths = @(
    "$env:appdata\*", 
    "$env:localappdata\*",
    "$env:temp\*"
)

foreach ($path in $tempPaths) {
    New-SmbClientBlockRule -Name "Block_$($path.Replace('\','_'))" 
    -Action $ruleAction -RemotePath $path
}

While effective against malware, these restrictions may break:

More surgical approaches that reduce collateral damage:

// Example: Allowlisting known good publisher certificates
$allowedCerts = @(
    "CN=Microsoft Windows, O=Microsoft Corporation, L=Redmond",
    "CN=Google LLC, O=Google LLC, L=Mountain View"
)

Get-ChildItem -Path "$env:appdata\*.exe" -Recurse | ForEach-Object {
    $cert = (Get-AuthenticodeSignature $_).SignerCertificate
    if ($cert -and ($allowedCerts -notcontains $cert.Subject)) {
        Write-Warning "Untrusted execution: $_"
        # Take mitigation action
    }
}

Additional layers to consider:

• Controlled Folder Access (Windows Defender feature)
• SRP (Software Restriction Policies) with hash rules
• Memory-based detection for suspicious process injections

For organizations implementing these restrictions:

1. Phase the rollout with test groups
2. Maintain detailed audit logs of blocked executions
3. Create exception processes for validated business needs
4. Combine with application control solutions like AppLocker

Modern ransomware like CryptoLocker frequently exploits writable user directories as execution points. These locations provide:

• Write permissions for non-admin users
• Low visibility for casual monitoring
• Path variability that bypasses simple path rules

Using Group Policy Objects (GPO):

Computer Configuration → Policies → Windows Settings → 
Security Settings → Software Restriction Policies → Additional Rules

Example GPO path rule for AppData:

Path: %AppData%\*.exe
Security Level: Disallowed
Description: Block EXE execution from AppData

Common applications affected by such restrictions:

Most enterprise AV solutions provide similar controls:

• Symantec: Application and Device Control policies
• McAfee: Access Protection Rules
• CrowdStrike: Execution Prevention policies

PowerShell script to audit potential conflicts:

# Find executables in protected paths
$paths = @("%AppData%","%LocalAppData%","%Temp%")
foreach ($path in $paths) {
    Get-ChildItem -Path $path -Filter *.exe -Recurse -ErrorAction SilentlyContinue |
    Select-Object FullName,LastWriteTime,Length |
    Export-Csv -Path "$env:USERPROFILE\Desktop\AppExecutionAudit.csv" -Append
}

For legitimate applications requiring execution from these paths:

1. Certificate-based allowlisting (preferred)
2. Hash-based rules (for static executables)
3. Path exceptions with strict ACLs