Question: Hello my server is getting hit by spiders from bingbot, google, yahoo, yandex, and some place in the UK all at the same time crashing it.

While I have no reason to think any one person did this, it strikes my odd that it happened all at the same time. 

Should I be worried? 

The only changes before this started was that I changed all the server passwords.

Answer: 
Bing, Google and Yahoo usually do not flood the the server with requests, but send far less than one request per second.

Please double check that you really get many requests from them within a very short time frame (e. g. within a second).

If your web application does have issues with handling occasional requests (for example on request per second), you can slow down Bing and Yahoo with the following entry in robots.txt:

```
Crawl-delay: 120

```

This will ask crawlers to wait at least 120 seconds between requests. For Google, you can define the delay in the [webmaster tools](http://www.google.com/webmasters/tools/).
It's crawling because of some link somewhere. You would need either to throttle bots or fix the websites so they are faster. Not sure about how to throttle the bots, you might want to check with google webmaster page or this:

<https://stackoverflow.com/questions/1328436/how-to-prevent-googlebot-from-overwhelming-site>