Today, when you look for a well-known application on Google, you are more than likely to find dozens of download links from different websites. Even top-ranking links hide a lot of dangers.

The presence of a signing certificate is in fact not enough for trust and so is the source of the download. An increasing amount of malware and malware injected software, signed with a legitimate digital certificate, is distributed by highly ranked websites without being detected. A practice that exposes internet users to a lot of risks.

To confirm this thesis and quantify the level of risk that the average internet user is exposed to, I verified the integrity of popular applications by downloading them from the official websites and other highly ranked ones and comparing the hashes of the downloads.

Is my download bonafide and untampered software? 

For my test, I used a very popular tool: PuTTY, the “as famous” open-source terminal emulator by Simon Tatham ( This tool counts millions of downloads and active users.

First, I installed CodeNotary Integrity Verification extension for Chrome by vChain. The extension protects internet users from installing malware, by automatically verifying the download unique hash to that of the official application, previously notarized with CodeNotary. If the hash does not correspond to the original, the user is altered so to avoid any dangerous installation. The extension is available here on the Chrome Web Store.

I, then, downloaded PuTTY from the official websites. The extension confirmed that the software was original, obviously.

Putty integrity check CodeNotary
Successful integrity check of PuTTY by CodeNotary Chrome Extension

Testing the integrity of PuTTY Downloads

I then moved on with testing downloads of PuTTY for top-5 links. I have to say that Simon Tatham is doing a better job at SEO, with the link to the official download website landing first in google search. Nevertheless, amongst the top-5 links, I could find other suspicious download links.

We clicked on the first link that looked from a respectable source:

Before doing that, we checked on McAfee Secure whether the website was a known malware publisher and the result was negative.

McAfee website verification
Results of McAfee verification of website trust

Also, in this case, vChain Chrome Extension immediately notified me that the file did not match to the version downloaded from official website resource.

In the case of PuTTY, McAfee WebAdvisor also alerted me to that I was about to download dangerous file suggesting me to interrupt the downloads. Ironically that was the same Antivirus software which just a few seconds before gave me green light on the website.

CodeNotary Integrity verification PuTTY
vChain Integrity verification of PuTTY download

What are the main takeaways?

1. When downloading a software be aware of malicious copies. Some are benign replicas, but others include malware or undesired software.

2. You cannot rely on how well a website score on SEO to trust software

3. Digital certificates do not protect you from malicious software

How CodeNotary Chrome extension protects from malware?

As I said at the beginning of my post, up until today there was no easy way for internet users to verify if a download had been injected of malicious code. Even manual checks on website reliability and digital signature proved to be insufficient for this task. In fact today it’s quite common to find malware signed with official and legitimate digital certificates.

CodeNotary Download Integrity Verification extension for Chrome protects users from installing malware whose names mock that of famous applications. No manual verification, no searching the web, the extension automated everything for you.

If you are a software developer or a software publisher and you want to protect your customers from downloaded malware injected clones, start now to sign your code with CodeNotary.  The solution is free for Open Source and Non-commercial project.