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Building a Better Moat: Designing an Effective Covert Red Team Attack Infrastructure

Building a Better Moat: Designing an Effective Covert Red Team Attack Infrastructure

Red team assessments are distinct from penetration tests in many ways, typically in assessment duration, tradecraft sophistication, and level of active incident response. If the assessment is so different, why would you want to use the same attack infrastructure you’d use on a penetration test? This talk will cover how to design and leverage an effective covert attack infrastructure. I’ll cover practical design considerations, demonstrate covert attack infrastructure concepts, and provide sample attack infrastructures. This talk will not cover the nitty-gritty HOW aspect of infrastructure deployment, focusing instead on the WHAT and WHY aspects.

@bluscreenofjeff

October 25, 2017
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  1. whoami
    Jeff Dimmock (@bluscreenofjeff)
    • Adversary Simulation Lead at SpecterOps
    • Adaptive Threat Division alumni
    • Avid blogger (https://bluescreenofjeff.com/)
    • Writes some Aggressor scripts
    • Speaker at BSides NoVA 2017 and HackMiami
    • Participated in Pacific Rim CCDC since 2014
    • Maintains the Red Team Infrastructure Wiki w/ @424f424f
    (http://github.com/bluscreenofjeff/Red-Team-Infrastructure-Wiki)

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  2. Agenda
    • Introduction
    • Design Considerations
    • General
    • Domains
    • Payloads
    • C2
    • SMTP
    • Example Infrastructure Designs
    • Key Takeaways

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  3. Standard Pentest Setup
    Victim Internet Team Server
    example.com
    Domain

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  4. Covert Red Team Attack Infrastructure
    domain1.com
    domain2.com
    domain3.com
    domain4.com
    Victim Internet Team Servers
    Domains Redirectors

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  5. Benefits of a Covert Infrastructure
    • Blends in with non-malicious infrastructure
    • Builds in defenses against Blue team
    • Resilience when an asset is blocked
    • Flexibility to adapt as the test progresses

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  6. • Segregate all assets based on function
    • Place a redirector in front of every asset
    • Blend in with normal traffic for the target
    • Configure assets in a way that individual pieces can be rolled
    • Keep the length of the test in mind when designing
    Design Considerations - General

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  7. • Don’t go overboard for your target
    • Tailor the design for anticipated or encountered obstacles
    • Evaluate infrastructure primitives before choosing one
    • Be fluid as the test goes; redesign as needed
    (Sidenote: document EVERYTHING)
    Design Considerations - General

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  8. Design Considerations - Domains
    • Always use categorized domains*
    • Pre-categorized vs. home-grown
    • Matching the target’s domain categorization can help blend in
    • Alternatively, organizations often have domain category
    whitelists (try Healthcare/Finance!)
    *unless emulating an actor who doesn’t

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  9. Design Considerations - Domains
    • Domains should match planned pretext
    • Good choices:
    ◦ Impersonate target company
    ◦ Similar to popular companies/services (Google, Microsoft,
    etc.)*
    ◦ Generalized domains that match industry
    *There are precedents for companies coming after squatters

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  10. Design Considerations - Payloads
    • Payload type
    ◦ HTA, LNK, PowerShell download cradle, etc
    • Delivery method (attached, web-based)
    ◦ Attachment
    ◦ Download link (server vs. cloud storage)
    • Access control options
    ◦ IP/fingerprint-based restrictions
    ◦ Expiring payload links

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  11. Design Considerations - Payload Redirection
    • “Dumb pipe”
    ◦ socat/iptables
    ◦ Forwards all connections
    ◦ No monitoring of requests
    • Filtering
    ◦ Apache mod_rewrite, nginx
    ◦ Perform conditional processing on requests
    ◦ Modify rulesets on the fly

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  12. Design Considerations - Command and Control (C2)
    • Longhaul
    ◦ Used to regain access
    ◦ Persistence
    ◦ Slow check-ins
    • Shorthaul
    ◦ Used for primary operating
    ◦ Burned frequently
    ◦ Faster check-ins
    • Number of servers

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  13. Design Considerations - Command and Control (C2)
    • Popular protocol choices:
    ◦ HTTP(S)
    ◦ DNS
    ◦ Domain Fronting (over HTTPS)
    ◦ Third-party

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  14. Design Considerations - Command and Control (C2)
    Attribute HTTP(S) DNS
    Domain
    Fronting
    Third-Party
    Latency Low High Medium Medium
    Likelihood to
    Work
    Average High High High
    Detectability Average High Low Low
    Ease of Blocking Average Low Low Low
    Ease of Setup Easiest Easy Medium Medium/Hard

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  15. Design Considerations - Command and Control (C2)
    • Traffic shaping:
    ◦ Custom network footprint
    ◦ Emulate a specific application or threat actor
    ◦ Modify potential signatures (URIs, user agents, etc.)
    ◦ Modify any host implant attributes as much as possible
    • Use custom profiles for each server

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  16. Design Considerations - Command and Control (C2)
    • Choose an appropriate protocol and redirection method per
    server
    ◦ Validate latency before launching the test
    • Keep servers separate
    ◦ Shorthaul and longhaul servers fulfill different roles
    ◦ Be disciplined with each server type
    ◦ Never cross the streams!
    • Don’t be afraid to roll new infrastructure

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  17. Design Considerations - C2 Redirection
    • “Dumb pipe”
    ◦ Easiest setup, no filtering protections
    • Filtering
    ◦ Longer setup, higher resilience
    • Domain Fronting/Third-Party C2
    ◦ Requires setup or development
    ◦ Blends in well
    ◦ Very hard to block

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  18. Design Considerations - SMTP
    • Self-setup
    ◦ Set up yourself
    ◦ DKIM, SPF, PTR records needed
    ◦ Can be time-intensive
    • Third-party
    ◦ Automatic reputation
    ◦ Anti-spam controls
    • Open Relay
    ◦ Can use target’s own server against them
    ◦ Anti-spam controls could get you flagged

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  19. Example Infrastructure Design #1
    • Email attachments blocked
    • Pre-phish revealed email appliances
    • Appliances crawl all links in emails
    • No intel about web browsing restrictions
    • Mixed OS environment

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  20. Example Infrastructure Design #1
    legit-files.com
    longhaul.com
    Payload
    Server
    Longhaul
    DNS C2
    iptables
    Redirector
    Apache Redirector
    (serving OS-specific
    payloads)
    If request matches appliance
    fingerprint, redirect to
    target’s real website
    *Shorthaul C2 and SMTP infrastructure not pictured

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  21. • About half of users don’t have internet access
    • Those with internet access are heavily restricted
    • Publicly-accessible OWA and remote access logins
    Example Infrastructure Design #2

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  22. Example Infrastructure Design #2
    legit-files.com
    google.com
    Payload
    Server
    Domain
    Fronting
    HTTPS C2
    Google App
    Engine Instance
    Apache Redirector
    Phishing link redirects to cred capture;
    login submission redirects to payload
    *Shorthaul C2 and SMTP infrastructure not pictured
    Cred
    Capture
    Server

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  23. Example Infrastructure Design #3
    • Email attachments blocked
    • Email appliance reviews all links and blocks wide range of file
    extensions
    ◦ docx allowed
    • Pre-phishing was manually acted on quickly
    • Found case study for the target’s deployment of a popular
    online storage service

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  24. Example Infrastructure Design #3
    legit-files.com
    dropbox.com
    Payload
    Server
    Third-party
    C2 Server
    Dropbox Folder
    Apache Redirector
    File extension rewrite &
    Expiring payload download links
    *Shorthaul C2 and SMTP infrastructure not pictured

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  25. Key Takeaways
    • Segregate assets
    • Use redirectors, ideally with filtering
    • Stress test assets for operational latency
    • Document EVERYTHING
    • Don’t go overboard - achieve your objectives

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  26. bit.ly/RedTeamInfrastructure
    specterops.io
    bsoj.co/ArcticCon2017

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