Trustwave SpiderLabs Exposes Unique Cybersecurity Threats in the Public Sector. Learn More

Trustwave SpiderLabs Exposes Unique Cybersecurity Threats in the Public Sector. Learn More

Managed Detection & Response

Eliminate active threats with 24/7 threat detection, investigation, and response.

Co-Managed SOC (SIEM)

Maximize your SIEM investment, stop alert fatigue, and enhance your team with hybrid security operations support.

Advisory & Diagnostics

Advance your cybersecurity program and get expert guidance where you need it most.

Penetration Testing

Test your physical locations and IT infrastructure to shore up weaknesses before exploitation.

Database Security

Prevent unauthorized access and exceed compliance requirements.

Email Security

Stop email threats others miss and secure your organization against the #1 ransomware attack vector.

Digital Forensics & Incident Response

Prepare for the inevitable with 24/7 global breach response in-region and available on-site.

Firewall & Technology Management

Mitigate risk of a cyberattack with 24/7 incident and health monitoring and the latest threat intelligence.

Offensive Security
Solutions to maximize your security ROI
Microsoft Exchange Server Attacks
Stay protected against emerging threats
Rapidly Secure New Environments
Security for rapid response situations
Securing the Cloud
Safely navigate and stay protected
Securing the IoT Landscape
Test, monitor and secure network objects
Why Trustwave
About Us
Awards and Accolades
Trustwave SpiderLabs Team
Trustwave Fusion Security Operations Platform
Trustwave Security Colony
Technology Alliance Partners
Key alliances who align and support our ecosystem of security offerings
Trustwave PartnerOne Program
Join forces with Trustwave to protect against the most advance cybersecurity threats
SpiderLabs Blog

Did I do that? (PenTest Faux Pas)

Many times, in the course of explaining what I do to others that are unfamiliar with information security and penetration testing, the question is eventually asked: "So, after you've broken-in, do you fix the problems?" At which point I get to say, "No, that's the best part. I only have to break it! Fixing it is someone else's job", although that's not entirely true, we always make good recommendations.

Experienced penetration testers rarely break things in the course of testing, but they all started somewhere. At some point, they all either have or will break something. In this post I'm going to review some of the common gotchas, faux pas, and unintentional mistakes that I've seen and experienced during pen tests over the years.

ARP Spoofing Gone Wild

This one is especially common for new pen testers or if someone is in a hurry and mistypes a network range. For example:

ettercap -Tq // //


ettercap -Tq /[gateway IP]/ //

This is a bad idea. Unless you're on some high performance hardware and a fast network link among a sparsely populated or low traffic network, trying to route all local network traffic through your box is generally a very bad idea. The likely result: you blackhole portions of the network, possibly including the local gateway. Clients don't like it when the network stops working. If you were performing the test remotely, you may not even be able to reconnect to your box to stop the problem. Always start with a small number of targeted hosts and watch your traffic like a hawk. You can see traffic statistics (including dropped packets) by hitting 's' from within ettercap's text interface.

My Pipe is Bigger than Yours

This one is a personal, true story. I was performing your basic run of the mill Man-in-the-Middle (MitM) attack between three hosts (that's all, only three) on the local network. Within a minute of beginning my ARP Spoofing, I got a call from my client that their web application was having problems and connections were getting dropped. I immediately stopped, re-ARPed my targets, and everything went back to normal. I pared my attack down to two hosts, and tried again, this time paying attention to my traffic stats. I got a call again from the client that the problem was back and I saw the problem: dropped packets were going through the roof. While I had the client on the phone, I asked them what kind of traffic their server usually handled and what was the size of the network pipe? It turns out, with a 100Mbit network interface, I was attempting to intercept and route a 2Gbit aggregate link -- that's right, I was trying to shove 4Gbits of traffic over a 100Mbit connection. Be mindful of your link speed and don't bite off more than your interface can chew.

One Guess Too Many

Excessive password guessing is something that's so obvious it shouldn't bear mentioning...unless you have multiple consultants, testing multiple environments that share common Windows domains. It becomes even more complicated when the different domains that are shared between these environments have different password policies: number of lockout attempts, lockout counter timeout and lockout duration. It's entirely possible to lockout an entire domain guessing just one password...if several consultants try it at once. Tread lightly, communicate with your partners, and know the password policies of the domains and systems being tested.

Out of Disk Space...

...Not you. Them. Whether it's a tool generating log data or tcpdump capturing packets, any process you start that writes to the disk of a compromised machine (ie. not your machine) has the potential to bring the system to a halt. Always watch the rate of growth of your logs and dump files and make sure that if you lose your connection to the machine, you can get back in and stop the process before it gets out of hand. Memory dumpers, especially, can eat up hard disk space quickly, if not handled with care.

Deus ex Machina

Sometimes things go horribly wrong and there is no good reason why. I have heard of cases where a simple port scan against some common, basic networking services caused the target system to crash. Or, where an enterprise-level web application that can service thousands of requests per second will freeze up if hit with more than 10 requests per second from the same source IP. In these cases, all you can really do is damage control. Don't panic, don't try to shift the blame, and offer any assistance you can in determining the cause of the problem. Be a part of the solution. Who knows, you may have just identified a potential bug or availability weakness.

Keeping It Clean

Cleaning up after yourself is an important part of pen testing. While these things often go unnoticed, sometimes forever, a client finding suspicious evidence left behind after a test just looks bad. I've seen old accounts left behind from prior pen tests, and heard of clients panicking when they discover password dumping tools after an Anti-Virus update that have been sitting quietly on a disk for years. Sometimes a tool gets whacked by AV mid-way through completion and temporary services get left behind or processes hang. Whatever the cause, keep notes, clean up and leave systems the way you found them.

Moral of the Story

In summation, there is one thing all of the above have in common: presence. If the client never knows you were there, you did it right.

Latest SpiderLabs Blogs

Important Security Defenses to Help Your CISO Sleep at Night

This is Part 13 in my ongoing project to cover 30 cybersecurity topics in 30 weekly blog posts. The full series can be found here.

Read More

2024 Public Sector Threat Landscape: Trustwave Threat Intelligence Briefing and Mitigation Strategies

Trustwave SpiderLabs’ 2024 Public Sector Threat Landscape: Trustwave Threat Intelligence Briefing and Mitigation Strategies report details the security issues facing public sector security teams as...

Read More

How to Create the Asset Inventory You Probably Don't Have

This is Part 12 in my ongoing project to cover 30 cybersecurity topics in 30 weekly blog posts. The full series can be found here.

Read More