Open ports which are accessible to the Internet at large are not "machine internals". If you do not want someone to access your systems, then you should configure your systems to not allow that access.

They are scanning 127.0.0.1 locally from the browser, so the ports do not need to be internet-accessible.

They are open ports which are accessible to the Internet at large. Or at least, any site you go to. If you don't like that there are various means to close off those ports to your browsers (Windows firewall, network namespaces, etc).

"It's not my fault I can break into your house and steal everything"

It is illegal for me to perform a portscan. Why it is legal for eBay, who knows?

Visiting a website implies consent.

Consent is a voluntary agreement to something. Port scanning is definitely not something I would expect when browsing the web (And based on the amount of upvotes on the last thread, not something most of HN would expect), so how can I be consenting to it without knowing about it?

What percentage of ebay visitors even know what portscanning is? How can somebody consent to something they aren't aware of, don't anticipate, and certainly don't even understand? Your notion of "consent" is an utter joke.

They might not know what port scanning is, but can they agree to "anti-fraud measures?"

Maybe they might agree to such anti-fraud measures, but I don't think they have. I don't consider 'ignoring the terms of use buried at the bottom of the page or in small print' a legitimate form of indicated consent.

Agree with you that simply putting something in the terms of use doesn't necessarily indicate agreement. If they're only doing it to signed in users, then presumably they had the terms put in front of them at some point, but I think your objection is still fair in any case.

To what extent do they need consent to port scan, though? They're not intending to do anything malicious, and in fact (assuming you are the owner of the account that's signed in) they're doing it partly to benefit you. Is there a law against port scanning? Does it affect users in any way?

What percentage of eBay users know what an IP address is?

Not in the GDPR.

GDPR allows "necessary" data processing for "legitimate interests". IANAL but I believe a non-damaging portscan to check for security issues to be allowed. Especially as eBay has the legitimate interest to ward off fraud - and customers have the legitimate interest to have their accounts protected.

> non-damaging protscan

Tell that to every corporation on Earth, especially to Banks, that "port scanning your perimeter is an innocent thing". Tell that your employer as well and do tell us what's your job status afterwards.

(I am not downvoting the utterly silly grey comments - I want them to be visible to a) ;)

Then they need to disclose that behavior. Because my firewall marks portscans as a malicious activity.

Since the portscan happens clientside on 127.0.0.1 I doubt your firewall will be able to notice the portscan.

That depends if you use IPv4 with NAT like almost everyone on a residential Internet uplink or IPv6 with a public routed address...

127.0.0.1 (aka localhost) isn't affected by your NAT setup. Your browser initiates this scan on the local loopback device, so the traffic will never even leave your computer (even on linux, it's somewhat difficult to get it to route 127.0.0.1 to another computer and it'll break a lot of applications in the process or make them insecure).

IPv6 with a public routed address still means there is a firewall, just like with NATv4. NATv4 just also has a NAT router with that firewall.