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.



October 25, 2017


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    whoami Jeff Dimmock (@bluscreenofjeff) • Adversary Simulation Lead at SpecterOps

    • Adaptive Threat Division alumni • Avid blogger ( • 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 (
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    Agenda • Introduction • Design Considerations • General • Domains

    • Payloads • C2 • SMTP • Example Infrastructure Designs • Key Takeaways
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    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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    • 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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    • 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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    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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    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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    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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    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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    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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    Design Considerations - Command and Control (C2) • Popular protocol

    choices: ◦ HTTP(S) ◦ DNS ◦ Domain Fronting (over HTTPS) ◦ Third-party
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    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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    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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    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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    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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    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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    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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    Example Infrastructure Design #1 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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    • 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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    Example Infrastructure Design #2 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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    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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    Example Infrastructure Design #3 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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    Key Takeaways • Segregate assets • Use redirectors, ideally with

    filtering • Stress test assets for operational latency • Document EVERYTHING • Don’t go overboard - achieve your objectives