I've been performing lots of speed tests lately due to, among some other random things, an Internet programming class and getting Google Fiber hooked up.

Then I realized that SpeedTest.net uses a Flash app; it kind of bothered me that I can't monitor the transmission contents in my browser's inspector tools like regular downloads. What is being downloaded and uploaded for such speed tests? What are the risks with speed tests? (Doesn't have to be SpeedTest.net-specific; maybe speed tests in general if they're not all so different.)

  • A note on Speedtest.Net specifically, they use a test file that they download and then upload part of it back up I believe. The servers it connects to are also volunteered and often not hosted by SpeedTest.Net themselves. Commented Feb 19, 2014 at 0:06

2 Answers 2


Internet speed test is not an attack vector per se.

Flash vulnerabilities might be an attack vector. If Speed test is downloading data from untrusted source - that might be attack vector as well.

XSS, SQLi, other web app vulnerabilities, that can be used on the speed test website, could also be further used to attack it's users.

  • Thanks. What is being transmitted to facilitate the speed test?
    – Matt
    Commented Feb 19, 2014 at 0:06
  • Probably just some dummy data with a known size. It could be real or random data.
    – Jervelund
    Commented Feb 19, 2014 at 0:14
  • 2
    I'm pretty sure they just use old credit card data from Target™ Commented Feb 20, 2014 at 0:59

Not a significant risk via Flash as of 2021. Flash has been deprecated. None of the major browsers – Chrome, Edge, Safari, Firefox – support it any more. The speedtest tools are now typically using HTML5.

HOWEVER, now there are native apps available/being pushed as replacements, which ARE a potential vector for malware. Tech such as Software signing mandates enforced by many OSes and mobile software distribution platforms, e.g. AppLocker and System_Integrity_Protection's Gatekeeper offer some protection, but are far from foolproof. And people are still conned into installing what is actually malware but purportedly will update their version of the Flash Player on their systems...

(Amusingly, stale info is all over.)

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .