LLMNR and NetBIOS-NS Spoofing with Responder

Published on 12 April 2020

Link-Local Multicast Name Resolution (LLMNR) and NetBIOS-Name Service (NBT-NS) are name resolution protocols that are enabled by default on Windows machines. They’re both used as a fallback for DNS. If a machine requests a hostname, such as when attempting to connect to a file-share, and the DNS server doesn’t have an answer – either because the DNS server is temporarily unavailable or the hostname was incorrectly typed – then an LLMNR request will be sent, followed by an NBT request. LLMNR is a multicast protocol and NBT-NS is a broadcast protocol.

Therefore, an attack can take place where an attacker responds to these requests with illegitimate requests. For example, directing the requesting user to connect to the attacker's machine where an authentication attempt will be made – disclosing hashed credentials for the targeted user.

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PrivEsc: Extracting Passwords with Mimikatz

Published on 08 April 2020

We recently published an article on using Incognito for privilege escalation as part of a short series on using Metasploit. In this article we’ll cover an alternative approach for privilege escalation – extracting plaintext credentials. Whilst incognito is generally easier to use, Mimikatz is powerful and flexible.

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Using Metasploit

Published on 06 April 2020

Metasploit is an exploitation framework. It’s a core tool of the penetration tester’s toolset and we use it for several of our vulnerability demonstrations, so it makes sense to write a quick “introduction to” for Metasploit. We’re going to look at the module system, navigating around, setting variables and running payloads.

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PrivEsc: Token Impersonation with Incognito

Published on 06 April 2020

Incognito is a tool which can be used for privilege escalation, typically from Local Administrator to Domain Administrator. It achieves this by allowing for token impersonation. As a local administrator can read the entirety of memory, if a domain administrator is logged in their authentication token can be stolen. We'll investigate its use here.

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Network Mapping with Nmap

Published on 03 April 2020

Before being able to determine if systems are vulnerable, it’s critical to first find as many active systems within the scope as possible and to accurately determine what services those systems expose. A common tool for use in network mapping is Nmap.

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Extracting Domain Hashes: Mimikatz

Published on 17 March 2020

We previously covered how to perform incredibly fast hashcracking with AWS. In this post we’ll take a step back, and look at one simple method to extract the hashes from a domain controller. To be clear, this is a post exploitation step and to perform these steps a domain administrator account will be needed.

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Hash Cracking with AWS

Published on 09 March 2020

In a previous post, I showed the steps to capture a WPA handshake and crack it using Hashcat. On my tiny travel laptop I achieved 416H/s, which is…slow.

AWS offers “GPU Optimized” EC2 instances:

  • g4dn.xlarge – $0.53 per hour
  • g3s.xlarge – $0.75 per hour
  • p3.16xlarge – $24.48 per hour (that’s ~$18,000 per month!)
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Bruteforcing Windows Accounts

Published on 24 February 2020

A common configuration on Windows Active Directory accounts is to have an account lockout threshold of say, 5 invalid attempts, and an observation window of 30 minutes. This is likely due to the fact that the “Suggested Setting” after setting a threshold is to enable a short observation window. As shown:

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Bruteforcing Kerberos

Published on 21 February 2020

It is possible to brute-force Windows accounts directly, using tools like Metasploit using modules such as smb_login, which will target port 445 (SMB). However, it’s also possible to brute-force the Active Director authentication protocol Kerberos directly.

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An Introduction to IPv6

Published on 17 February 2020

IPv6 is not new, RFC1883 discussed the protocol back in 1995. However, it has been updated several times, becoming a Draft Standard with RFC2460 in 1998, and an Internet Standard with RFC8200 in 2017!

If you’re wondering if there was an IPv5 the answer is sort of, in the Experimental Internet Stream Protocol, Version 2 (ST-II) which used the IP version number 5 within its packet header, that’s RFC1190. IPv7 was sort of RFC1475, IPv8 was sort of RFC1162, and for an April fools joke we go IPv9 in RFC1606.

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Kerberoasting

Published on 17 February 2020

Any domain user within Active Directory can request a service ticket (TGS) for any service that has an SPN (Service Principal Name). A part of the service ticket will be encrypted with the NTLM hash of the target user, allowing for an offline bruteforce attack.

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ASREP Roasting

Published on 16 February 2020

If an Active Directory user has pre-authentication disabled, a vulnerability is exposed which can allow an attacker to perform an offline bruteforce attack against that user’s password.

This attack is commonly known as “AS-REP Roasting” in reference to Authentication Service Requests, a part of the process of authentication with Kerberos. An attacker who is able to find a user with pre-authentication disabled can request an AS-REP ticket for that user and this will contain data encrypted with the user’s password.

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