eBay is port scanning your system when you load the webpage

Martin Brinkmann
May 25, 2020
Updated • May 25, 2020

Have you been to eBay lately? The auction site is a popular destination to buy new and used items. It may surprise you that eBay is running a local port scan when you access the site in a browser.

I verified the port scan on ebay.com and ebay.de using built-in developer tools of several web browsers. It is likely that other eBay sites will also run the port scan.

ebay port scan

You can verify this easily. Use a browser such as Google Chrome, Firefox, Brave, Microsoft Edge or Vivaldi. Open a new Tab page and hit the F12 button to open the Developer Tools of the web browser. Switch to the Network tab in the Developer Tools and load the eBay website in the browser's address bar.

Wait for the page to load and look for in the name in the list of connections. These are the scans that eBay performs when you connect to the site.

You can click on the connection to look up additional information; doing so reveals the port that is scanned by eBay. The scan is run by check.js, a JavaScript that is executed on eBay when users connect to the site. It uses WebSockets to perform the lookups on the local system using the specified port, and the scans occur regardless of sign-in state.

Bleeping Computer created a handy table that lists the ports:

Program Ebay Name Port
Unknown REF 63333
VNC VNC 5900
VNC VNC 5901
VNC VNC 5902
VNC VNC 5903
Remote Desktop Protocol RDP 3389
Aeroadmin ARO 5950
Ammyy Admin AMY 5931
TeamViewer TV0 5939
TeamViewer TV1 6039
TeamViewer TV2 5944
TeamViewer TV2 6040
Anyplace Control APC 5279
AnyDesk ANY 7070

Most of the ports are used by remote desktop applications such as VNC, Teamviewer, or Windows Remote Desktop. The eBay name is an abbreviation of the remote desktop software.

Nullsweep, the site that reported the issue first, discovered that the port scans were not run on Linux client systems.

ebay firefox port scan

It is unclear why eBay is running the port scans. A likely explanation is that it is done to combat fraud, e.g. by taking over a computer, establishing a remote desktop connection and either making purchases on eBay, through fake auctions, or other means.

Reactions on Twitter and other social media sites are negative for the most part. Users criticize eBay for scanning ports at all, and for scanning ports of users who are not signed in to the site.

What you may do about it

If you don't want your systems to be port scanned by eBay whenever you connect to the site, you may be able to do something about it.

  1. Block the check.js script in a content blocker.
  2. In some browsers, e.g. Firefox, disable Web Sockets.

The eBay site loads the check.js script from the following URL currently: https://src.ebay-us.com/fp/check.js

Something like ||src.ebay-us.com^*/check.js should work.

The URL may change and it is different when you connect to localized eBay sites, e.g. eBay.de.

The other option, to disable WebSockets entirely, may lead to incompatibilities and loading issues on sites. Still, it is possible in Firefox by setting the parameter network.websocket.max-connections to 0.

Now You: What is your take on this? (via Born)

eBay is port scanning your system when you load the webpage
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eBay is port scanning your system when you load the webpage
The auction site and marketplace eBay is running port scans on user systems when the eBay website is opened in a web browser.
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  1. ilev said on August 4, 2012 at 7:53 pm

    Doesn’t Windows 8 know that www. or http:// are passe ?

    1. Martin Brinkmann said on August 4, 2012 at 7:57 pm

      Well it is a bit difficulty to distinguish between name.com domains and files for instance.

    2. Leonidas Burton said on September 4, 2023 at 4:51 am

      I know a service made by google that is similar to Google bookmarks.

  2. VioletMoon said on August 16, 2023 at 5:26 pm

    @Ashwin–Thankful you delighted my comment; who knows how many “gamers” would have disagreed!

  3. Karl said on August 17, 2023 at 10:36 pm


    The comments section under this very article (3 comments) is identical to the comments section found under the following article:

    Not sure what the issue is, but have seen this issue under some other articles recently but did not report it back then.

  4. Anonymous said on August 25, 2023 at 11:44 am

    Omg a badge!!!
    Some tangible reward lmao.

    It sucks that redditors are going to love the fuck out of it too.

  5. Scroogled said on August 25, 2023 at 10:57 pm

    With the cloud, there is no such thing as unlimited storage or privacy. Stop relying on these tech scums. Purchase your own hardware and develop your own solutions.

    1. lollmaoeven said on August 27, 2023 at 6:24 am

      This is a certified reddit cringe moment. Hilarious how the article’s author tries to dress it up like it’s anything more than a png for doing the reddit corporation’s moderation work for free (or for bribes from companies and political groups)

  6. El Duderino said on August 25, 2023 at 11:14 pm

    Almost al unlmited services have a real limit.

    And this comment is written on the dropbox article from August 25, 2023.

  7. John G. said on August 26, 2023 at 1:29 am

    First comment > @ilev said on August 4, 2012 at 7:53 pm

    For the God’s sake, fix the comments soon please! :[

  8. Kalmly said on August 26, 2023 at 4:42 pm

    Yes. Please. Fix the comments.

  9. Kim Schmidt said on September 3, 2023 at 3:42 pm

    With Google Chrome, it’s only been 1,500 for some time now.

    Anyone who wants to force me in such a way into buying something that I can get elsewhere for free will certainly never see a single dime from my side. I don’t even know how stupid their marketing department is to impose these limits on users instead of offering a valuable product to the paying faction. But they don’t. Even if you pay, you get something that is also available for free elsewhere.

    The algorithm has also become less and less savvy in terms of e.g. English/German translations. It used to be that the bot could sort of sense what you were trying to say and put it into different colloquialisms, which was even fun because it was like, “I know what you’re trying to say here, how about…” Now it’s in parts too stupid to translate the simplest sentences correctly, and the suggestions it makes are at times as moronic as those made by Google Translations.

    If this is a deep-learning AI that learns from users’ translations and the phrases they choose most often – which, by the way, is a valuable, moneys worthwhile contribution of every free user to this project: They invest their time and texts, thereby providing the necessary data for the AI to do the thing as nicely as they brag about it in the first place – alas, the more unprofessional users discovered the translator, the worse the language of this deep-learning bot has become, the greater the aggregate of linguistically illiterate users has become, and the worse the language of this deep-learning bot has become, as it now learns the drivel of every Tom, Dick and Harry out there, which is why I now get their Mickey Mouse language as suggestions: the inane language of people who can barely spell the alphabet, it seems.

    And as a thank you for our time and effort in helping them and their AI learn, they’ve lowered the limit from what was once 5,000 to now 1,500…? A big “fuck off” from here for that! Not a brass farthing from me for this attitude and behaviour, not in a hundred years.

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