The 404 errors are because of other sites linking to you?– MrWhiteDec 2, 2013 at 14:59
Yes. If I click on the "Linked From" tab in Google Webmasters after selecting a particular 404 error, it shows a list of all these sites that supposedly have on link on their site to a page or directory on my site. These pages and directories all have some sort of viagra reference but don't exist. Some of the worst site offenders have domains like: burundichina, dendenboy, hdjxzh, kyawsint, etc. I know some of this stuff just takes time to clear, but I go from like 300+ crawl errors to 30 and then back up to a few hundred. I'm worried there's still some vulnerability I haven't caught.– user1491394Dec 2, 2013 at 17:07
I don't know why removing the infected content would necessarily decrease the 404 errors - that looks like coincidence to me. How did you blocked referers? What HTTP status code did you return? Presumably you would have seen this type of error increase in GWT? It might be a never ending battle to block these sites, but a 404 would be the correct response IMO. It's the requests from these sites that don't result in a 404 that are the problem. In a hacked site these requests could result in a 30x redirect, sending the unsuspecting visitor to the malicious site.– MrWhiteDec 3, 2013 at 23:31
Blocking by referrer won't help: Googlebot doesn't send a referrer header when it crawls, so it will never see your block.
Here is what Google's John Mueller (who works on Webmaster Tools and Sitemaps) has to say about 404 errors that appear in Webmaster tools:
HELP! MY SITE HAS 939 CRAWL ERRORS!!1
I see this kind of question several times a week; you’re not alone - many websites have crawl errors.
- 404 errors on invalid URLs do not harm your site’s indexing or ranking in any way. It doesn’t matter if there are 100 or 10 million, they won’t harm your site’s ranking. http://googlewebmastercentral.blogspot.ch/2011/05/do-404s-hurt-my-site.html
- In some cases, crawl errors may come from a legitimate structural issue within your website or CMS. How you tell? Double-check the origin of the crawl error. If there's a broken link on your site, in your page's static HTML, then that's always worth fixing. (thanks +Martino Mosna)
- You don’t need to fix crawl errors in Webmaster Tools. The “mark as fixed” feature is only to help you, if you want to keep track of your progress there; it does not change anything in our web-search pipeline, so feel free to ignore it if you don’t need it. http://support.google.com/webmasters/bin/answer.py?answer=2467403
- We list crawl errors in Webmaster Tools by priority, which is based on several factors. If the first page of crawl errors is clearly irrelevant, you probably won’t find important crawl errors on further pages. http://googlewebmastercentral.blogspot.ch/2012/03/crawl-errors-next-generation.html
- There’s no need to “fix” crawl errors on your website. Finding 404’s is normal and expected of a healthy, well-configured website. If you have an equivalent new URL, then redirecting to it is a good practice. Otherwise, you should not create fake content, you should not redirect to your homepage, you shouldn’t robots.txt disallow those URLs -- all of these things make it harder for us to recognize your site’s structure and process it properly. We call these “soft 404” errors. http://support.google.com/webmasters/bin/answer.py?answer=181708
- Obviously - if these crawl errors are showing up for URLs that you care about, perhaps URLs in your Sitemap file, then that’s something you should take action on immediately. If Googlebot can’t crawl your important URLs, then they may get dropped from our search results, and users might not be able to access them either.
The 404 errors that Google reports are for your benefit. If they are not actually problems that need to be corrected, you don't need to do anything about them.
That's kinda what I thought (+1). I did just wonder, however, if the high number of spam-keyword-like backlinks from hacked sites could possibly have a negative SEO effect? Or, as I suspect, the fact that these links return a 404 counteracts that?– MrWhiteDec 4, 2013 at 22:02
My big concern right now actually isn't even the SEO, I get nervous seeing hundreds of 404 errors in this way because this same thing preceded the spam attack. I'm sure I removed any infected code from my site, so I shouldn't be sending out any spam links showing up as 404s. Will I just have to wait this out until these spammers (link farms, whatever they are) move on somewhere else? Dec 5, 2013 at 0:07
1@w3d spam keywords linking to 404 pages shouldn't hurt. But you might not want to "claim" those links by redirecting them to real pages. Dec 5, 2013 at 2:08