Not illegal. Sites like shodan.io would have an issue if it was.
Shodan is outside your network's firewall, therefore only able to access services you've exposed to the wider web.
If I understand the article, the websocket scan eBay is doing is trying to connect to local listeners on your laptop, behind your network's firewall and possibly even behind your laptop's firewall.
It does not, however, sound like an attacker can establish arbitrary TCP connections (at least using the technique from the article). Instead, the attacker can determine if something is listening on a port because it will take a different amount of time to negotiate/drop a connection to a port when there is a listener than when there is not a listener.
In other words, this sounds like a variant of a timing attack. As such, presumably, this particular avenue of attack can be mitigated by the browser vendor inserting a delay s.t. no information can be gleaned from how long it takes to negotiate/drop a websocket connection.
EDIT: I also wonder if it would be possible to do a similar port scan using the timing of XHR requests to localhost (e.g. http://localhost:[port]).
Maybe not, but what if the ports you have open actually are HTTP servers for development purposes? In that case wouldn't a website be able to crawl your unreleased work, and/or mess with what you're doing, with requests seemingly "out of nowhere"?
One time, I port scanned my public IP (of my ISP) from an EC2 box, and I got an email from EC2 saying they received an abuse complaint from the ISP for port scanning activity.
Legitimate usage from researchers and people reading about infrastructure they have the right to do security testing on may be a larger percentage than you think.
What percentage of torrent traffic do you suppose - or better have stats for - is not copyright infringing? I'd think it's about 0%.
Would certainly be interested if you can prove that's wrong.
- Monitoring your own network or that of your clients for exposed ports
- Researching Internet topology, or performing aggregate queries like “how many nginx servers are connected to the Internet”
Can you use it maliciously? Yes. But, most of the time, if you have a target it would make more sense to do the port scan yourself. And if you’re just dragnet searching for vulnerabilities, most you find will probably already have been exploited. Sites like shodan are good for the overall health of the web because they force website owners to maintain security posture. If you know that foregoing a wordpress upgrade means you’re one script kiddy with a shodan account away from getting hacked, you’re going to keep your site up to date. This saves you from script kiddies, but also from the more sophisticated hackers who would run a port scan themselves anyway.
Any legitimate security service is going to be doing there own scans, surely.
Statistics, yes, but I can't see those stats being especially good. You could probably get equally good nGinx data from netcraft, who IIUC get the data from http responses banners on :80 :443.
I'm not sure I buy the "security posture" line, isn't it circular. Tools to help crack your site are good because it means to have to have counter-measures to combat tools for cracking your site?
Only legitimate use of port scanning for me has been testing access to my own/clients computers, I feel. That's not too say I've not used it for illegitimate things ...
1. External network monitoring: know what you have connected to the Internet and get notified if anything changes unexpectedly. This has actually gotten significantly more challenging with services deployed to the cloud where your IT department might not even know which IPs to keep track of.
2. 3rd-party risk assessment: understand the security exposure of your partners, vendors, supply chain or other 3rd-parties. For example, lets say you're an insurance company that wants to provide cyber insurance. Shodan data can help you understand what sort of risk you'd be taking on. The data has also been used in M&A as part of due diligence to get a metric on the security of the IT department of the company they're thinking of acquiring.
3. Market intelligence: basically Netcraft on steroids. Shodan doesn't just have web information but also for many other protocols. This information is used by hedge funds and vendors to understand which products are purchased and deployed to the Internet. The data is skewed due to the nature of public IPs but there are still things you can do.
4. Policy impact: get a measure for how policies at the country-level are impacting Internet connectivity. For example, the OECD used Shodan to get a measure of Internet-connectivity per capita.
5. Fraud detection: is your customer trying to make a purchase from a machine that's been compromised? Or running a a VPN/ proxy? Shodan is used in transactional fraud detection to flag suspicious payments.