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You are here: Home / Archives for phishing attack

phishing attack

How Phishing Websites Use Captcha to Fool Browsers and People

October 30, 2020 By Craig Hays Leave a Comment

Reading Time: 5 minutes

Evading detection and building trust with Captcha challenges and Smishing attacks.

EE Smishing, phishing and a captcha form
The latest SMS Phishing message I’ve received from not-my-real phone company

This week I received another SMS Phishing attack which was almost identical to the previous Smishing attack covered. There were two things that struck me as particularly interesting this time:

  1. The attack used the s.id Indonesian link shortening service
  2. The attack used a Captcha page to limit access to the phishing page to real people only

Thinking about the first point, it’s clear that s.id, the “World’s shortest URL shortener”, has been chosen to minimise the size of the links in the phishing text message. I would guess that they’re also not particularly quick about removing malicious links (but I could be wrong).

The second point, the use of a Captcha form after clicking on the link in the text message, is interesting to me in three ways.

Phishing site asking you to ‘please prove that you are not a robot’

1. Using Captcha to Block Malware Detection

Without a doubt, preventing the automatic detection of the phishing page on the website is the primary reason for hiding it behind a Captcha challenge.

Captcha is almost short for ‘Completely Automated Public Turing test to tell Computers and Humans Apart’. This is a convoluted way of saying ‘if you can read this sign you’re a human and I’ll let you in.’ The premise is that computer image recognition is still not good enough to accurately decipher the words in the image and therefore only people can pass the test.

What that means for automated malware scanners is that they can’t see the phishing pages that innocent people are being sent links to.

Automated Phishing Site Detection

There are a lot of people trying really hard to detect and block phishing pages in as many places as possible before they cause actual people actual harm. Tools such as Microsoft ATP and Google Safe Browsing to name just two automatically fetch and scan web pages and score them against a constantly evolving set of rules in order to determine if they’re real or fake.

When a malicious website is detected it is added to the naughty-list and any time someone tries to access that site it is either blocked or they are shown a warning message like this:

Google Chrome deceptive site ahead warning message
A suspicious website warning from the Google Chrome browser

Phishing sites usually run on commodity phishing kits – pre-packaged software bundles designed specifically for stealing and saving sensitive information without getting caught. As they’re so widely and consistently used, they’re really easy to detect. When a website has replica EE branding all over it and it isn’t the real EE domain, it’s obviously a fake site.

Fake EE phishing site hidden behind a Captcha form

By hiding the phishing kit behind a Captcha page it prevents automated scanners from analysing it. This means they can’t be automatically added to the naughty-list and users could be Captcha-ing themselves into an unsafe site without realising it.

As soon as a user sees a warning message like the one ‘Deceptive Site’ one above, it’s usually game over for that particular phishing attack. Staying under the radar by evading detection means that once the user passes the Captcha challenge, there’s a high probability of a successful phish attack being completed.

2. Captcha as an Accidental Credibility Indicator

As a weird byproduct of blocking automated scanners, adding a Captcha page gives a phishing site a weird sense of credibility in the eyes of some users. Most of the time, when we see Captcha forms, it’s to protect something we care about from harmful robots. For example, Captcha is used to prevent bots from brute-forcing our passwords and gaining access to our online accounts.

When we see Captcha forms we have a habitual response to trust what they’re doing. It’s not particularly strong, but it’s there. For many, the context within which it appears will be enough to override any sense of ‘this is fine’. Some of the less cyber-aware people on the internet won’t see what we see. This is the target market for a phishing campaign like this.

3. It Isn’t Even Mobile-Ready!

This is the bit I find the most infuriating. The attack could have been so much better but it let itself down!

The phishing or smishing attack was delivered by text message directly to my smartphone. It’s a mobile-only attack vector and yet the Captcha part of phishing kit isn’t even mobile ready!

While I cropped the image to make it readable in the earlier screenshot, I left the alignment and spacing as is. In fact, on my smartphone it actually looked like this:

I’ve still cropped the bottom of the image as it was ridiculously long and with a very small font…

Look how small that is!

It baffles me how attackers can be so on-the-money about one thing such as evading automatic detection and yet be clueless about how the attack is presented to the end-user. Had this been mobile-ready with a responsive layout that matched the shape and size of the screen, this entry point would have been so much more effective.

We can see that attackers and their tactics are evolving and improving over time. Next time the Captcha form might be better integrated. Next time they might even attempt to fake ‘Multi-Factor Authentication’ me since they already had my phone number to begin with. All I know is that they’re willing to experiment and get creative about future attacks in order to increase the likelihood of a payout as much as possible.

Also, Sorry DataHubClub!

(It looks like your CMS was compromised and used for this attack. I hope you get that sorted quickly. From Googling the name and domain, I suspect it’s just a dead DNS entry that’s pointing to a cloud server that someone has spun back up and taken advantage of. You’ve probably not been hacked at all… but who knows…)

Phishing Email to Company Devastating Ransomware in 5 Hours

October 25, 2020 By Craig Hays 2 Comments

Reading Time: 6 minutes

How hackers manually escalated from a malicious email to a devastating, company-wide ransomware takeover in under 5 hours.

It started with a phish ransomware in 5 hours
Photo by Pixabay from Pexels

(This article aims to contextualise an excellent incident report by Thedfirreport.com. I’ve used my own experience to fill in the gaps to demonstrate how these attacks affect real people in real companies.)

The Attack Started Like Many Others

A phishing email landed in the victims inbox at around 5 pm UTC and was promptly opened and read. There was nothing particularly suspicious about it. It was a well-written email with a reasonable call to action. There were no urgent demands. It wasn’t claiming to be from the company CEO. It looked identical to many of other emails received that same day.

The company email servers scanned it and allowed it straight through to the victim’s inbox. It was sent through a legitimate and well-known email delivery service with a good reputation. There were no attachments to be scanned for malware. All it contained was a politely written request and a link to a web page.

The web page didn’t ask them to log in. It wasn’t trying to steal their password by masquerading as a trusted login page. All the victim saw was a message saying: ‘Oops! The document preview isn’t available. Click here to download’, or words to that effect. This is the sort of error message that we’ve all seen many times over the years. Most of us wouldn’t think twice about clicking that link, myself included.

Malware In Disguise

The browser downloaded a file named something like PreviewReport.DOC.exe. A warning message came up at the bottom of their browser asking if the user wanted to keep or discard the file as it could be harmful.

Regrettably, our unfortunate user downloads all sorts of documents all day every day and many of them give the exact same warning. They’ve learned that this warning message is just a regular part of online life. One more thing they must click on in order to get work done. Out of habit, they clicked on ‘keep’, then opened the file.

The executable was signed with a trusted certificate from a well-known vendor. It was malicious, and yet it was signed. The thing is, anyone can buy legitimate and trusted software signing certificates on the internet these days if you know where to look. The user’s PC had AppLocker configured to block unsigned executables but it made no difference. The trusted, signed malware executed without a problem.

Their local antivirus software had the latest virus signatures downloaded and available. As the malware was unique to this victim, the signature didn’t match anything on record. Nothing was blocked.

As far as the user was concerned, the file did nothing. Perhaps it was corrupted. Nevermind…

Sadly, it wasn’t corrupted. It sent a message out to a command and control server on the internet to say, ‘Hello, I’m here, And I’m waiting’, then opened a backdoor into the heart of the company network. It checked-in using standard, encrypted, HTTPS traffic, and notified the ransomware gang that it was active and waiting for instructions. From the outside, it looked exactly the same as the device’s owner viewing any other secure web page on the internet.

[Read more…] about Phishing Email to Company Devastating Ransomware in 5 Hours

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