tl;dr sec is a newsletter about AppSec and scaling security, automated bug finding, conference talk and paper summaries, and useful links from around the web. You can subscribe here and see past issues here.

Being Powerful While Powerless, Sadcloud, and Bugcrowd’s Asset Inventory Service


This week’s tl;dr sec is coming to you live, from Tel Aviv! That’s right, live, I’m typing this up as fast as I can, so don’t scroll down too quickly, or you’ll see a blank page and it’ll be embarrassing.

I’m here because I was invited to give the closing keynote at DevSecCon Tel Aviv, which was exciting, as it’s my first keynote! 🎉 To be honest, I was a bit nervous, but it seemed to be well-received and there were some great questions afterwards.

I enjoyed the talks and met some sharp people. I’ll share some of my notes over the next few weeks.

If you'd rather read this newsletter on our blog, you can read it here.
📜 In this newsletter...
  • Tools: an SSH multiplex backdoor, intentionally vulnerable AWS infrastructure for training.
  • Talk: Owning the Cloud through SSRF and PDF Generators.
  • Misc: learn quantum mechanics from a comic strip, a tale of the cyber security version of Theranos.
  • Asset Inventory: Thoughts on Bugcrowd's new offering and two more companies in the space.
New Summary:
In this Global AppSec Amsterdam 2019 talk, Gusto security engineer Nathan Yee describes his experiences and lessons learned on how to be effective as the only AppSec engineer at a start-up, without a senior title.
🔗 Links


sadcloud - A tool for spinning up (and down) intentionally vulnerable AWS infrastructure using Terraform, built by Rami McCarthy and Joshua Dow of NCC Group (blog post).

Similarly, in case you haven’t already heard about it, is another great hands-on AWS security resource by Scott Piper, who I recommend following if you’re into cloud security.

SSHession - an SSH multiplex backdoor tool released by NCC Group, useful for red teams. Described more in this blog post: Bypassing Authentication on SSH Bastion Hosts.

Owning the Cloud through SSRF and PDF Generators

(Slides) This talk by Ben Sadeghipour and Cody Brocious, presented at DEFCON, Global AppSec DC, and ShellCon, has neat tips and tricks on some more advanced SSRF scenarios, for example, attacking headless browsers and HTML renderers. Worth a read if you do web app security testing.

Example content:

  • Problem: metadata or internal IPs are getting filtered
    • Solution: Use a custom domain like and point it to the asset you are trying to access ( ->
  • Problem: Only able to use whitelisted domains
    • Solution: Find an ‘Open Redirect’ on the whitelisted domain(s) and use that to exploit your SSRF
  • Problem: SSRF is there but I can’t see the output
    • Solution: Use Javascript and exfil data


“The Talk” by SMBC - a hilarious comic strip about a mother giving her son the… quantum computing talk. I guarantee you’ll laugh (and learn something).

A Cybersecurity Firm’s Sharp Rise and Stunning Collapse
A long piece on how the company Tiversa ended up being like a Theranos for the security industry - charismatic leader and fraud, served with a side of extortion. No movies on it yet (hello, Netflix readers 😉).

Asset Inventory III: Revenge of the Shadow IT

tl;dr: Bugcrowd is offering an “Attack Surface Management” service, where their researchers will do asset inventory for you. Makes sense for Bugcrowd to offer given their current resources. This approach has some pros, but I’m unsure if they’ll be able to incentivize consistent, continuous good coverage.

As we’ve seen in tl;dr sec #8, #9, and #10, asset inventory is a hot space right now. Bugcrowd is now joining the fray with their product “Attack Surface Management” (announcement blog post, product page).

As far as I can tell, the service is basically just paying some of Bugcrowd’s researchers to do asset discovery for you. My initial thoughts on this approach:


  • Keeps up with new asset discovery techniques as security tools and methodologies evolve.
  • (In theory) Can handle acquisitions, shadow IT, and other edge cases where “internal” solutions may fail, where you need to provide an AWS access key or otherwise have some level of control over the infrastructure; you can’t also do this, for example, in massive international companies with distributed development and IT teams.
  • (For Bugcrowd) They can leverage their existing resources (researchers) without having to build out new software that could be time-intensive and complex.


  • I’m unsure of how complete and rigorous coverage will be for one’s exposed attack surface over time. More on this below.

The open secret about bug bounty (is it even a secret?) is that while platforms tout how many researchers they have (“We have 1 BILLION expert hackers ready to…”), most of the accounts are probably inactive.

Of the active accounts, most are either script kiddies or people who report issues like, “By right-clicking on your web page I can view your site’s source code. Hacked! Bug bounty plz.” I’d guesstimate most bug bounty platforms have at most a few thousand competent security professionals that semi-regularly report bugs, with maybe 100-200 people who are excellent.

So given how limited active, knowledgeable bug bounty researchers there are, I’d be curious to see how Bugcrowd plans to effectively incentivize them to continuously monitor companies’ externally facing attack surface.

To me, for a researcher, it seems like the incentive would be more to do a deep, thorough job as soon as a company registers for this service, make some quick $$$, then check back in quarterly or after a big event like an acquisition. Maybe the top researchers will just set up some automated scripts and periodically check the results, as I’ve heard some already do for detecting website changes that indicate new or modified functionality.

It will be interesting to see Bugcrowd’s long term plans for this service. Will they attempt to observe the processes and methodologies of their top researchers working for the service, then use their engineering team to build out a more production-ready, scalable version and cut out the middle men? Like Lyft and Uber working hard to build autonomous vehicles.

…and one more thing
Other asset inventory companies include Assetnote and, who focus on monitoring companies’ external attack surface. (Thanks David Scrobonia and JB Aviat)

⭐️ New Summary

In this Global AppSec Amsterdam 2019 talk, Gusto security engineer Nathan Yee describes his experiences and lessons learned on how to be effective as the only AppSec engineer at a start-up, without a senior title.

I liked this talk because it discusses common challenges that resonate with many security teams:

  • Given a preciously finite amount of security engineer time, how do you scale the security team’s visibility and impact in a company?
  • How do you effect organizational change when you can’t lean on a director-level title?


Nathan was the first security hire at Gusto, and for awhile, the only security team member.

  • He was just an independent contributor (IC) without a senior title, so he had little power to officially “force” people to do anything.
  • He was outnumbered by developers 100 or 150 to 1 (this is pretty common in my experience).
  • As it was a high-growth start-up, the company’s priorities and goals were constantly changing, which he needed to keep up with.

Nathan was fundamentally limited by his finite amount of time, so the question he asked himself was:

How do you scale yourself across developers and non developers alike?

Nathan discusses two core types of strategies: technical and cultural, and concludes with two examples of nice security wins that happened because of the positive security culture he helped build.

Technical Strategies

The technicial strategies he described are pretty standard: “shifting left” with continuous static analysis (brakeman), scanning for vulnerable dependencies, penetration testing, and bug bounty.

Here are some of the unique tidbits/comments:

  • Modern security teams are significantly higher leveraged when they can write code, calling out Dino Dai Zovi’s 2019 Black Hat USA keynote.
  • Another huge value of being able to code, which I think is often underappreciated, is being able to speak the language engineers use every day is incredibly powerful. You can work together as partners on the “same side” with a common vocabularly.
    • It gives you empathy into what developers’ lives and perspectives are, enabling you to better align your needs and goals witih their workflow.
    • Being able to build security features for engineers or push code that fixes a security bug also earns you their respect- you’re committing code too, not just pointing out flaws.
  • Nathan created a custom check that will send him a Slack message automatically whenever any PR touches a brakeman.yml file, which contains the set of bugs whitelisted by brakeman. This gives him continuous visibility into how scan results are being addressed over every repo without having to manually examine every commit.
  • One of the core values of lightweight scanning tools like brakeman or linting tools, beyond the issues they identify, is that they give developers fast feedback. Giving timely results is critical (vs sending them results about code they wrote days ago, where they’ve lost the mental context).
  • With brakeman scanning every commit for common bug classes, developers can write and push code at their own speed, without being blocked on waiting for an AppSec engineer’s time.
  • Review your pen test reports over time as a gauge of how you’re doing; hopefully the number and severity of findings is trending down over time.

Cultural Strategies

Build Relationships with Key Stakeholders

Including IT, compliance, product managers, legal, engineering, and infrastructure.

  • IT can be the front line of security, e.g. “I clicked on a sketchy link and now my browser is acting weird.”
  • Befriending product managers is key because it helps you insert security into feature planning itself. Also, when they trust you, they’ll proactively inform you when there are upcoming plans to touch security-relevant functionality, such as authentication, authorization, etc.
    • These inbound heads-up are incredibly useful, because the security team can’t join every sprint planning meeting or really even be aware of what all of the different dev teams are working on.

Be Open and Vulnerable

Share the results of bug bounty submissions and pen test reports with developers. Show them your successes, be open about your challenges and failures.

This openness will build trust with developers and make them want to help you.

Be Accessible

When Nathan was the only security team member, he made an effort to eat lunch with a different team every day. That helped him, and the team members, put faces to names and start building rapport.

Preemptively Fill Up the Security “Trust Bank”

Take advantage of opportunities, however small, to help out, provide value, and build trust with developers and other parts of your company before you need it.

Once Nathan took the time to help a developer who was having trouble with 2FA on a personal (non-Gusto) account. This wasn’t work-related, nor would it fall under the security team’s purview if it was, but Nathan took the time to help him figure it out.

This freely offered help, with no intent of a corresponding favor, ended up generating good will that was crucial several months later when Nathan had a big security-related ask of this person.

“You’re going to need to make security withdrawals from various accounts at some point; put in the upfront deposits to make those as seamless as possible.”

Security Education

An hour of teaching web security to 15 devs takes one hour of his time, but then they go off to their respective teams with security on the top of their minds.

A benefit of training, beyond the knowledge shared, is that it allows Nathan to put a face to names for devs and makes them aware that security is a friendly team within the company that they can reach out to.

Wins from a Positive Security Culture

In one case, Nathan had an engineer proactively reach out, saying that a certain group appeared to be overprileged.

Since engineers are in the trenches day-to-day building the software your company runs, they generally have the best context of how systems work in detail as well as what level of access users and groups should need to perform their required tasks. Being able to lock down this group was a great win.

In another example, a developer proactively reviewed HackerOne reports from the night before, determined that they were real issues, and then submitted PRs fixing them about an hour later.

Nathan didn’t have to badger anyone to review HackerOne repors or convince them of the value of fixing the bugs, they proactively went from triaging through fixing the vulnerabilitiess all on their own.

Final Takeaway

“Relying on a CSO or Director title to influence is a problem that positional power doesn’t solve. True power comes from a desire to understand and solve challenges with software and relationships.”

✉️ Wrapping Up
Have questions, comments, or feedback? Just reply directly, I'd love to hear from you.

If you find this newsletter useful and know other people who would too, I'd really appreciate if you'd forward it to them🙏

Thanks for reading!


@clintgibler | @programanalysis


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