Friday, January 12, 2018

It's W2 scam season


Time for a short Friday afternoon social engineering‍ discussion. If you work in HR / finance / benefits, you'll want to stick with me.

It's January, the beginning of tax season in the US (and I presume, other countries as well). Employers in the US are required to provide W2 statements documenting pay and tax to their employees by the end of his month.

Scammers know this, and love to exploit this annual ritual. The common schemes I see are an email or phone call pretending to be from either a company executive (often the CEO or CFO), or from the taxing authority, with an urgent request for employee records.

Urgent because, a sense of urgency can short-circuit skepticism and get an employee to respond before thinking.

Oddly, even though employers must provide this data by January 31, W2 scams have tended to peak around March for the last few years. Perhaps there's a psychological element since individual tax returns are due by April 15 so it remains top of mind for the HR/finance/benefits/payroll employee.

If you work in HR / finance / payroll / benefits, or otherwise have access to employee personal data, stay vigilant over the next 90 days or so. Be suspicious of any request for employee records, especially if it comes in an unusual manner.

Take the time to verify the request through a trusted channel. Depending on your organization size, that might mean in person, over the phone, or via an established business process.

DON'T ship a CSV or XLS of employee data simply because someone - even the CEO - sends an email requesting such.

If you own or manage a business, or manage those that have access to employee records, be sure they know how employee records are handled, and know the appropriate process for requesting and approving transfer of that data.

If there is no established process for handling employee records - make one, and stick to it.

Wednesday, December 20, 2017

A handy trick for proxying HSTS sites in Chrome


TL;DR: Chrome has a nifty undocumented trick that makes proxying so much more useful when testing sites using HSTS or pinned certs: where the security warning screen doesn't give you an option to ignore, type "badidea" to continue anyway.

Browser makers have been raising the bar when it comes to website security, gradually moving toward a state where insecure websites stand out like a sore thumb. The result has been a steady increase in the proportion of websites that safeguard your private information while in transit between you and the web server. Google's Chrome in particular makes it especially challenging to use badly secured websites, with a variety of warning messages such as the image above.

In the example above, the website in question has enabled HTTP Strict Transport Security, or HSTS, which tells browsers that it should only be accessed over a secure channel, and so to always use HTTPS. Essentially, the website tells browsers "don't ever come here again except over HTTPS."

In this case, the warning is slightly misleading: I am browsing to the site over HTTPS, but using a proxy to inspect what I am sending to the website. The proxy feature of Burp Suite allows me to send information to a secure website, but to catch and decrypt it before it leaves my computer, to see exactly what my browser is sending.  

As a penetration tester or vulnerability researcher, it is very handy for making sure an application is not sending more data than I intend. It is also very handy for probing an application for data leaks and weaknesses. In this scenario, Chrome's helpful protection is less, well, helpful.

Thankfully, Google developers included an undocumented Easter Egg: typing the phrase "badidea" while that warning is on the screen, will clear the warning and proceed to the website.

A note to readers: this is a handy trick for researchers and penetration testers. Generally though, that warning is there for a reason. If you unexpectedly see a warning that your connection is not private - your connection is not private. If you are not intentionally man-in-the-middling your connection, the warning likely means either the website or your network is compromised. The technique I use for testing web applications is the same technique used by malicious hackers to eavesdrop when you connect to an "evil twin" hotspot mimicking the legitimate connection provided by your coffee shop or airport.

The moral? Unless you know what you are doing, bypassing Chrome's privacy warning is, well, a bad idea.

Thursday, November 30, 2017

Private data in public places


Professional social engineer and open source intelligence expert Stephanie "@_sn0ww" Carruthers makes a living out of (mis)using what people and companies share publicly, so when she talks I listen. Her talk at the Lonestar Application Security conference in October was captivating in showing how such information can be used to infiltrate a business (in her case, for the purposes of showing the business their weaknesses and how to defend themselves against someone with actual malicious intent). She made an observation this week that sparked some lively discussion:

Don't leave your resume public on google docs.

Monday, November 27, 2017

Be sure to deregister Amazon devices purchased as gifts

Buying Amazon devices as holiday gifts? Be sure to deregister them from your account!

Now that post-Thanksgiving shopping is in full swing, here's a brief tip for those purchasing Amazon gadgets as Christmas gifts: if you are giving an Amazon Device to someone outside your household, take a moment to deregister the device from your Amazon account. Otherwise you may inadvertently give more gift than you bargained for.

Amazon devices ship pre-connected to the purchaser's account -- and thus to the purchaser's payment settings. This is the the case for Fire TV devices; it may also be true for Fire tablets and Echo voice control devices. Straight out of the box, an Amazon Fire TV device can purchase digital media and games, billed to the original purchaser of the device.

I actually like this user experience decision: it is quite consumer-friendly, making it simple to unbox it, plug it in, and immediately start using it. Sure there's a potential abuse case here: a device stolen out of the mailbox could be abused to make digital purchases billed to the rightful owner - but those purchases are still tied to your account, not to the device, so there's no transferable value to the thief*. On top of that the purchaser gets a notification as soon as the device is first activated, limiting the window to make fraudulent purchases. And of course fraudulent purchases can be disputed and reversed.

This leads to another tip: where possible use a low-limit credit card, or a prepaid debit card, for any online accounts. That way any fraud is with the bank's money and not yours. A debit card is tied directly to your bank account, meaning fraud immediately hits your cash balance. Sure, you'll get fraudulent transactions reversed and the money back. Eventually. But eventually doesn't help if the rent is due today.

*Digital media is not transferable. However, some apps feature in-app shopping, suggesting it may be possible for a mail thief to plug in a Fire TV and purchase physical items for delivery. Alexa voice commands theoretically would allow for purchasing hard goods independent of any app features.

Thursday, November 9, 2017

IR Toolkit

In 20 years of systems administration and incident response, there are a handful of tools I find myself coming back to over and over again. Naturally, the SysInternals suite is on the list, along with Wireshark and Didier Stevens PDF tools. I've also included portable installations of Python Some are useful for examining a system, others are useful for examining a suspicious file or attachment. So... I started a GitHub project to document my favorite free and/or open-source tools.

I'll bet my readers have some of their own favorites: by all means, please comment below, or submit a pull request on GitHub, and I'll update the list!

Tuesday, October 10, 2017

Exploiting Office native functionality: Word DDE edition

Sensepost researchers show a way to exploit DDE to run code from Word, without macros or buffer overflows. Here's how to detect it.

Updated 20 October: Added a note regarding enabling full command line logging for process creation events; added a note clarifying that "Creator Process Name" is only recorded in Windows 10 and Windows Server 2016. Older versions of Windows record the creator process ID but not the process name; added references to a variety of exploitation techniques found by other researchers or seen in the wild.

Updated 11 October: I originally wrote that this exploit technique bypassed both disabled macros, and Protected View. That is incorrect: this technique will work if macros are disabled, but the code does not trigger while in Protected View. Thanks to Matt Nelson (@enigma0x3) for pointing out my mistake.

I love reading exploit techniques that rely on native features of the operating system or common applications. As an attacker, I find it diabolically clever to abuse features the target fully expects to be used and cannot turn off without disrupting business. As a defender, I am intrigued by the challenge of detecting malicious use of perfectly legitimate features.

Researchers Etienne Stalmans and Saif El-Shereisuch of Sensepost wrote of a slick way to execute code on a target computer using Microsoft Word - but without the macros or buffer overflows usually exploited to this end. Instead, they use dynamic data exchange, or DDE - an older technology once used for coding and automation within MS Office applications. This is particularly clever because it works even with macros disabled - because it's not using the macro subsystem.

Thursday, October 5, 2017

Enable two-factor on your Yahoo account... if you can

Yahoo! accounts have very different security options depending on their origin.
Unless you've been living under a rock, you know by now that Yahoo! suffered a massive data breach in 2013. The number of accounts reportedly affected changed a number of times, until this week it announced that every single account had been compromised. All 3 billion of them.

Zack Whittaker, security editor for ZDNet, had this to say:

Secure your Yahoo account with 2FA, but do not delete it. Deleting it will recycle your account after 30 days — and anyone can hijack it.

That's good advice - if you can. Many cannot.

Whois David?

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I have spent the better part of two decades in information technology and security, with roots in application developer support, system administration, and network security. My specialty is cyber threat intelligence - software vulnerabilities and patching, malware, social networking risks, etc. In particular, I strive to write about complex cyber topics in a way that can be understood by those outside the infosec industry.

Why do I do this? A common comment I get from friends and family is that complex security topics give them headaches. They want to know in simple terms how to stay safe in a connected world. Folks like me and my peers have chosen to make a profession out of hacking and defending. I've been doing this for the better part of two decades, and so have a high degree of knowledge in the field. Others have chosen different paths - paths where I would be lost. This is my effort to share my knowledge with those that are experts in something else.

When not in front of a digital screen, I spend my time raising five rambunctious teens and pre-teens - including two sets of twins. Our family enjoys archery, raising show and meat rabbits, and simply enjoying life in the Texas hill country.

For a decade I served as either Commander or a division leader for the Awana Club in Dripping Springs, Texas; while I have retired from that role I continue to have a passion for children's ministry. At the moment I teach 1st through 3rd grade Sunday School. Follow FBC Dripping Springs Kids to see what is going on in our children's ministries.