Exploitation of hacked websites for cryptocurrency mining is a new thing, and it gets more popular day by day. Hacking websites for fun or other reasons like spamming, other exploitation is a thing of the past. All previous exploitation methods of hacked sites are outdated, have low-profit margins (except stealing of CC credentials and similar data) and incompatible with the modern trends. Now everyone wants cryptocurrencies, everyone obsessed about crypto money and everyone is ready to do anything to get it.
Mining requires time. More time means more calculations and hashing done. Only some specific sites could offer more extended visitor sessions, for example, websites that allow their users to watch movies online. Also, you can try to mine cryptocurrencies on more than one site to increase the exploiting rate, and this has recently been a source of great interest to hackers.
Coinhive has changed the behavior of hackers
Exploiting of previously hacked websites
There are signs that some of the hackers repeat their intrusion into previously hacked websites to remove any proof of hack and leave the site entirely functional but now equipped with cryptocurrency mining software. As I mentioned before, mining requires time, but if you split your mining code into tens, hundreds or even thousand websites you’ll get quite powerful mining net and this opportunity is attractive to the hackers.
For anyone who owns a website with average traffic Coinhive could be uninteresting, besides this involves risks to lose some audience due to ruined user experience if throttling set to a high level. But a hacker can run the miner on a dozen of websites it can achieve a sufficient mining rate virtually without any risk.
Since it’s hard to trace cryptocurrencies and owners of cryptocurrency wallets, all this stuff sounds like an endless Christmas for hackers.
How to identify and what to look for in the source code
The easiest way to identify that your PC is doing something more than usual is to pay attention to its performance. Cryptocurrency mining requires a lot of calculation power, and it means your PC CPU performance for other normal operations will decrease. In other words, your computer will be slower.
Another pretty good measure is to pay attention to how the computer tries to cool down itself. A lot of calculations require more electricity and generates way more heat. If your CPU fan or fans suddenly started to work at full throttle just a few seconds after a particular site loaded, it’s more likely that you’re already running a Coinhive or similar miner in your browser.
Proof of Work Captcha
Well, this may sound nice, but I doubt that it is designed purely as a challenge-response test and capable to reliably determinate user type. Anyway if it is used only as CAPTCHA so why not, but I tried this Proof of Work Captcha on an old and slow PC, and it required a lot of time, so users with slower PC’s will get poor user experience.
On the other hand, if this “Proof of Work Captcha” can protect websites from brute force attacks or spamming by using the CPU resources of the attacker PC to generate you some cash you might be interested in this CAPTCHA alternative.