You are probably reading this because you are a responsible regular user of the Diseases Database whose access has been denied.
Site defences may block innocent users if they share a proxy server or netblock with bot infected machines, hackers or abusers. This is unfortunate but service levels of our site depend on this capability. These protection mechanisms may deny access to entire internet service providers or institutions including prominent educational and healthcare establishments.
Certain automated web page downloading software applications (robots or 'bots') cause a site like ours difficulties if counter-measures are not taken. The Diseases Database has over 100,000 potential pages. Due to limited bandwidth on our side, rapidly downloading all (or a large proportion) of our pages impairs other user's access.
Our site would suffer dozens of partial outages per day if unprotected. This issue is not unique to smaller sites - the 'brown-outs' and intermittent losses of service often experienced on prominent sites are frequently the consequence of malware robots.
Denial of service is seldom the intent of badly designed robot software but often the outcome. Those responsible don't consider the consequences of bandwidth hogging. In the unlikely event a miscreant reads this we ask them to please desist. The average broadband user typically has more bandwidth than a small business web server. Some web sites may be capped or pay their ISP per kilobyte uploaded (although thankfully not ours). That's all there is to it. It's not big and not clever to bring down web sites and doing so might even hinder the malware author's illicit purpose.
Please find further explanation of our rationale below.
Please do not attempt to download the Diseases Database web site for off line use.
See also http://en.wikipedia.org/wiki/Offline_reader
We block the following...
Comment spam, referrer spam and spam sent to our published e-mail addresses is antisocial and annoying but not the main issue. Rather the associated bot ripping through the entire site while harvesting or delivering payloads may lead to bandwidth saturation.
Ironically web server vulnerability scanners are often dismally written and unchecked will loop for days repeatedly downloading a small set of pages.
This class of software pre-emptively downloads all links from a page 'in case' you want to look at them http://en.wikipedia.org/wiki/Web_accelerator
The principle of accelerators is arguably bogus: if you have good bandwidth you don't need one; if you have poor bandwidth they waste it and often anticipate the user's next action wrongly. Please turn them off and do yourself, us and the web in general a favour.
The Diseases Database is engineered to be highly responsive to individual requests - also our pages are small enough to race along a piece of wet string. On the other hand some of our pages have several hundred internal links and downloading all of them near simultaneously causes problems.
We routinely block several anonymous proxy services.
We acknowledge legitimate uses for (and users of) anonymous proxies. However an audit of Diseases Database hits revealed most (of many) accesses via Tor over a three month period were by illegitimate bots (largely comment or referrer spammers).
Please access the Diseases Database site either directly / via a standard proxy or else flee now: if your government or employer is so oppressive they object to our content you have bigger problems to deal with =:-0
Few of the major search engine robots consume excessive bandwidth.
Spiders which misbehave are banned politely via our robots.txt file. If this directive is ignored the blocking mechanism kick in.
PCs can be infected by malware. We thank you for ensuring your PC is not inadvertent host to these.
Otherwise if you find yourself blocked the probability is you unknowingly follow in the wake of incidents of abuse by other users or machines. It is almost impossible to trigger the defences with anything remotely resembling normal web browsing behaviour. It is difficult to invoke them deliberately even with insider knowledge using a conventional browser.
Some language translation services appear to "read ahead" like web accelerators; (unusually) proxy servers (e.g. those for mobile phones) can also be configured to do this. However both these facilities are frequently hijacked as portals for hacking and malware attacks so it is hard to determine what is happening.
We invite and very much welcome reports of "false positive" blocks and we have both the means and strong motivation to fix or work around these.