Google has a lot of built in protection for its users. Every search result page is filtered to provide a variety of answers whenever possible. Their system also tries to filter out websites that you might consider worthless.
Our own analysis has shown us that Google is constantly re-crawling jewelry websites. Some days, they download dozens or hundreds of pages per site, and other days they only look at 3 or 4 pages. Most of the time, they simply peek at a page to see if anything is different, and then they move on.
Google also monitors for hacked websites. Since they are crawling your website a few times a day, it's very likely that they would know your website is hacked before you do. We're not sure how quickly they take action, but we do know that if they discover a hacked website, they will attempt to block the site from showing up in the SERP.
Your computer is probably smart enough now to work with Google and provide an obnoxious red warning screen if you stumble upon a hacked website.
Google routinely looks at all the websites hosted on a single IP address. Inexpensive hosting companies will have up to 10,000 websites running on a single server with a single IP address. If one of those sites is hacked, there is a chance the rest could be vulnerable.
In this way, Google can provide another level of security to users. However, there is something else that Google looks for when scanning websites on a single IP address...
Large hosting companies will sell their service to anyone willing to pay. If they only charge $5 per month, they will probably need to have at least a few hundred websites on a single machine to cover their costs. Hosting companies typically don't care who uses their service: could be a jewelry store, could be a mechanic, could be an adult website, could be the current politician running for office.
Google expects to find an equal verity of websites on any single IP address. However, they also track when there is a higher percentage of spam or deceptive websites hosted on a single IP address, and someone on Google's anti-spam team will investigate to make sure the hosting company is not directly participating in spam, or that they are not supporting a spam company. Either way, all the websites hosted on that single IP address are likely to be removed from Google's index.
For your own website, the best protection you can give yourself is to make sure your hosting company is PCI compliant, and that they do not host any spam websites. You should also pay the extra money every month for a dedicated IP address. With a dedicated IP, you are assured that Google will not accidentally remove you from their index simply because you live next to a cyber criminal.