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Beyond the Pentest: How C2, Internal Pivoting, and Data Exfiltration Show True Risk

Your vulnerability scanner reports that there are no issues on your network. A pentester has spent the last week trying to exploit every system your organization owns with no luck. The check box for this year's compliance audit has been checked. While it is good that these things occurred, they do not complete the picture in regards to true risk.

Real attackers do not solely rely on software exploits to compromise an environment. In almost every breach you hear about the root of the compromise came from a phishing attack. This is why additional tests, post-infection, should be performed to assess just how far an attacker can go after gaining a foothold into your environment.

What command and control channels are available for an attacker to utilize to communicate with your internal systems? How easy is it for an attacker to move laterally within your environment and gain access to other systems? What are your detection capabilities when it comes to sensitive data being exfiltrated out of your environment? How do you test these attacker techniques using open-source tools?

This lecture will address these questions and more, including a showcase of attacker methodologies.

Beyond the Pentest: How C2, Internal Pivoting, and Data Exfiltration Show True Risk

  1. 1. Beyond the Pentest How C2, Internal Pivoting, and Data Exfiltration Show True Risk Beau Bullock
  2. 2. Beyond the Pentest What does a standard internal network pentest already cover? Port scans Vulnerability scanning Manual validation Provide recommendations
  3. 3. What is Wrong With This Attackers don’t vulnerability scan - too noisy Misses some very critical vulnerabilities Doesn’t account for domain systems already compromised
  4. 4. whoami Beau Bullock Pentester at Black Hills Information Security Host of Hack Naked TV Previously an enterprise defender OSCP, GXPN, GPEN, GCIH, GCFA, OSWP and GSEC
  5. 5. What Are We Missing Three major things Command and Control Internal Pivoting Data Exfiltration
  6. 6. How Do We Test These Start with the basics Standard domain user account Lowest level of access typically provisioned Standard system build Anyone on leave? Steal their system Standard network access
  7. 7. Command and Control
  8. 8. Command and Control Three focus areas Payload delivery Email, web, etc. Client-based protections AV, application whitelisting, HIDS, etc. Network-based protections Egress filtering, IDS/IPS, inline payload detonation
  9. 9. C2: Payload Delivery What can be emailed to your employees? Executable PDF Word DOC or XLS w/ macro Batch file Encrypted ZIP Extensionless files?
  10. 10. C2: Payload Delivery Protip: Many webmail services scan attachments for malware Some don’t allow EXE’s altogether Yahoo’s MTA does not scan, and allows EXE’s Use a third-party mail client to send through Yahoo
  11. 11. C2: Payload Delivery What can be downloaded? How about browser or Java or Adobe exploits? Are users allowed to insert USB drives?
  12. 12. C2: Client-Based Protections Did anything detect the payload after entry? Anti-Virus Application whitelisting SIEM alerts
  13. 13. C2: Client-Based Protections Payload types Non-encoded EXE Encoded EXE ShellCode injection Word Doc w/ macro Software exploit Physical access (rubber ducky)
  14. 14. C2: Client-Based Protections Bypassing Client-based protections Veil-Evasion Framework for creating custom malware PowerSploit Shellcode injection directly into memory Obfuscation
  15. 15. C2: Network-Based Protections Was the C2 channel detected? Firewall block IDS/IPS detection Inline Detonation
  16. 16. C2: Network-Based Protections What does an outbound portscan reveal? Weak egress filtering provides more legroom for C2 DLP might miss items not sent over standard ports
  17. 17. C2: Some Typical C2 Channels Standard TCP HTTP/HTTPS DNS ICMP
  18. 18. C2: C2 Through A Web Proxy Meterpreter Reverse_https Uses proxy settings on system PowerShell Empire!!! Same as above but in PowerShell Appears as web traffic through your web proxy
  19. 19. C2: C2 Over Social Media Can your users get to any social media sites? Twittor - Uses Twitter direct messages as a C2 channel GCAT - Uses Gmail as a C2 channel Sneaky-Creeper - Uses Twitter, Tumblr, and Soundcloud as a C2 channel
  20. 20. C2: C2 over DNS DNScat Tunnels traffic through DNS requests C2 channel through NS Records C2 even with EVERY port blocked outbound from the client
  21. 21. C2: C2 over ICMP Invoke-PowerShellICMP Tunnels traffic through ICMP echo-requests and echo-replys ICMP is commonly allowed through firewalls
  22. 22. Internal Pivoting
  23. 23. Internal Pivoting Use built-in tools as a low level user to compromise a network No vuln scans needed Less noise Escalate privileges; locate sensitive data
  24. 24. Pivot: GPP Passwords May 13, 2014 – MS14-025 Passwords of accounts set by GPP are trivially decrypted! …by ANY authenticated user on the domain Located in groups.xml files on SYSVOL
  25. 25. Pivot: GPP Passwords First thing I check for on an internal assessment Almost always find an admin password here Find it with: PowerSploit - Get- GPPPassword Metasploit GPP Module Or… C:>findstr /S cpassword %logonserver%sysvol*.xml
  26. 26. Pivot: Privilege Escalation Local privilege escalation Are we already a local admin? PowerUp Invoke-AllChecks looks for potential privilege escalation vectors
  27. 27. Pivot: Misconfigured Systems Occasionally, admins get lazy… and do things like add “Domain Users” group to the “Local Administrators” group
  28. 28. Pivot: Misconfigured Systems This means EVERY domain user is now is an administrator of that system Veil-PowerView Find-LocalAdminAccess Veil-PowerView Invoke-ShareFinder
  29. 29. Pivot: Password Spraying Domain locks out accounts after a certain number of failed logins Can’t brute force Solution: Try a number of passwords less than the domain lockout policy against EVERY account in the domain
  30. 30. Pivot: Password Spraying Lockout Policy = Threshold of five Let’s try one password across every account What passwords do we try? Password123 Companyname123 SeasonYear C:>@FOR /F %n in (users.txt) DO @FOR /F %p in (pass.txt) DO @net use DOMAINCONTROLLER IPC$ /user:DOMAIN%n %p 1>NUL 2>&1 && @echo [*] %n:%p && @net use /delete DOMAINCONTROLLERIPC$ > NUL
  31. 31. Pivot: Password Spraying
  32. 32. Pivot: LLMNR & NBTNS Poison LLMNR = Link-Local Multicast Name Resolution NBT-NS = NetBIOS over TCP/IP Name Service Both help hosts identify each other when DNS fails
  33. 33. Pivot: LLMNR & NBTNS Poison
  34. 34. Pivot: LLMNR & NBTNS Poison SpiderLabs Responder Inveigh PowerShell Script The result is that we obtain NTLM challenge/response hashes Crack hashes
  35. 35. Sensitive Data Hunt
  36. 36. Sensitive Data: Info Disclosure on Shares Sensitive files on shares? Find them with PowerView ShareFinder then FileFinder FileFinder will find files with the following strings in their title: ‘*pass*’, ‘*sensitive*’, ‘*admin*’, ‘*secret*’, ‘*login*’, ‘*unattend*.xml’, ‘*.vmdk’, ‘*creds*’, or ‘*credential*’ 
  37. 37. Sensitive Data: Locate RDP Jump Hosts Where are users RDP’ing to? Can provide insight into where critical systems are Get-NetComputers | Get-NetRDPSessions | Export- Csv –NoTypeInformation rdpsessions.csv
  38. 38. Sensitive Data: Virtualization Hypervisors
  39. 39. Data Exfiltration
  40. 40. Data Exfiltration What are organizations concerned about leaving their networks?  PCI data Patient health information Personally Identifying Information Intellectual property
  41. 41. Data Exfiltration How can attackers get data out of your network?  Email Web Access USB Drive Photo
  42. 42. Data Exfil: Email For email is DLP being enforced on the following? Cleartext in email body Encoded in email body Attachments Optical Character Recognition
  43. 43. Data Exfil: Web Is all web traffic subject to DLP inspection? Same types of tests as email are performed but tracking over standard and non-standard web ports
  44. 44. Data Exfil: USB Drives Are files allowed to be copied to a USB drive? Encryption DLP Blocked completely
  45. 45. Putting It All Together
  46. 46. Attack Scenario Target Organization Setup Firewall only allows outbound traffic through web proxy AV up to date on clients Email gateway allows Doc files Local Administrator account is widespread with same credentials
  47. 47. Attack Scenario Phishing email is crafted with Word doc attachment Word doc is weaponized with a Macro Email is sent to target employee
  48. 48. Attack Scenario Employee opens email Downloads attached .doc Enables content Macro runs PowerSploit PowerShell script to inject Meterpreter Reverse_https into memory Meterpreter C2 channel is established
  49. 49. Attack Scenario Password spray from the command line Spring2016? Run Find-LocalAdminAccess to find where the users are local admin Pivot using psexec
  50. 50. Attack Scenario Attacker dumps local user hashes (including local admin) Local administrator credential is not randomized Using PowerView UserHunter the attacker finds where Domain Admins are located
  51. 51. Attack Scenario Attacker pivots to DA workstation Runs Mimikatz to dump creds from memory Locates sensitive data with PowerView ShareFinder Exfils data
  52. 52. Summary
  53. 53. Summary What are the benefits of this style of testing? Real test of detection and incident response Shows how an attacker can go from low access to owning the environment Shows true risk to the organization
  54. 54. Thank You! @dafthack