2件事:

服务器层解决方案:mod_eveful(如果你使用apache)

http://www.zdziarski.com/projects/mod_evasive/

前端解决方案:反向验证码，或其他非侵入式验证码

http://www.ccs.uottawa.ca/webmaster/reverse-captcha.html

我不能百分之百地确定这是否可行，至少不尝试一下是不行的。

But it seems as if it should be possible, although technically challenging, to write a server-side HTML/CSS scrambler that takes as its input a normal html page + associated files, and outputs a more or less blank html page, along with an obfuscated javascript file that is capable of reconstructing the page. The javascript couldn't just print out straightforward DOM nodes, of course... but it could spit out a complex set of overlapping, absolute-positioned divs and paragraphs, each containing one letter, so it comes out perfectly readable.

机器人将无法阅读它，除非它们使用完整的渲染引擎和足够的人工智能来重建人类将看到的内容。

然后，因为这是一个自动化的过程，您可以根据您的计算能力经常重新打乱站点-每分钟，或每十分钟，或每小时，甚至每次页面加载。

当然，写这样一篇含糊不清的文章会很困难，而且可能不值得。但这只是一个想法。

首先，让我回顾一下我们需要做的事情。我意识到我只是在转述最初的问题，但重要的是我们要百分之百地理解这个问题，因为有很多很好的建议，4个中有2个或3个是正确的，但正如我将演示的那样，您将需要一个多方面的方法来满足所有的需求。

要求1:摆脱“机器人抨击”:

首页的快速“猛击”正在损害网站的性能，这是问题的核心。这种“猛击”既来自单ip机器人，也可能来自僵尸网络。我们想把两者都去掉。

要求二:不要破坏用户体验:

我们可以通过实施一个讨厌的验证程序来有效地解决机器人的情况，比如打电话给操作员，解决一堆验证码，或类似的问题，但这就像强迫每个无辜的飞机乘客跳过疯狂的安全圈，只是为了抓住最愚蠢的恐怖分子的渺茫机会。哦，等等，我们真的这么做了。但让我们看看在woot.com上能否做到这一点。

要求三:避免“军备竞赛”

正如您所提到的，您不希望卷入垃圾邮件机器人军备竞赛。因此，您不能使用隐藏或混乱的表单字段、数学问题等简单的调整，因为它们本质上是可以简单地自动检测和规避的模糊度量。

需求4:挫败“警报”机器人:

这可能是您的要求中最困难的。即使我们可以进行有效的人类验证挑战，机器人仍然可以在你的首页上投票，并在有新报价时提醒编剧。我们也想让那些机器人变得不可行。这是第一个需求的更强版本，因为机器人不仅不能发出破坏性能的快速请求——它们甚至不能发出足够多的重复请求来及时向脚本人员发送“警报”以赢得报价。

好，让我们看看是否能满足这四个条件。首先，正如我提到的，没有一种测量方法能达到目的。你将不得不结合一些技巧来实现它，你将不得不忍受两个烦恼:

少数用户将被要求经历重重考验 少数用户将无法获得特别优惠

我知道这些都很烦人，但如果我们能让“小”的数字足够小，我希望你会同意利大于弊。

第一个措施:基于用户的节流:

这个很简单，我相信你已经做过了。如果用户已登录，并保持每秒刷新600次(或其他)，您将停止响应并告诉他冷却。事实上，你可能会更早地限制他的请求，但你明白我的意思。这样，一个登录的机器人将被禁止/节流一旦它开始投票你的网站。这是简单的部分。那些未经验证的机器人才是我们真正的问题，下面就来谈谈它们:

第二个措施:某种形式的知识产权限制，正如几乎所有人都建议的那样:

No matter what, you will have to do some IP based throttling to thwart the 'bot slamming'. Since it seems important to you to allow unauthenticated (non-logged-in) visitors to get the special offers, you only have IPs to go by initially, and although they're not perfect, they do work against single-IP bots. Botnets are a different beast, but I'll come back to those. For now, we will do some simple throttling to beat rapid-fire single-IP bots. The performance hit is negligable if you run the IP check before all other processing, use a proxy server for the throttling logic, and store the IPs in a memcached lookup-optimized tree structure.

第三种方法:用缓存的响应掩盖油门:

With rapid-fire single-IP bots throttled, we still have to address slow single-IP bots, ie. bots that are specifically tweaked to 'fly under the radar' by spacing requests slightly further apart than the throttling prevents. To instantly render slow single-IP bots useless, simply use the strategy suggested by abelenky: serve 10-minute-old cached pages to all IPs that have been spotted in the last 24 hours (or so). That way, every IP gets one 'chance' per day/hour/week (depending on the period you choose), and there will be no visible annoyance to real users who are just hitting 'reload', except that they don't win the offer. The beauty of this measure is that is also thwarts 'alarm bots', as long as they don't originate from a botnet. (I know you would probably prefer it if real users were allowed to refresh over and over, but there is no way to tell a refresh-spamming human from a request-spamming bot apart without a CAPTCHA or similar)

第四项措施:

You are right that CAPTCHAs hurt the user experience and should be avoided. However, in _one_ situation they can be your best friend: If you've designed a very restrictive system to thwart bots, that - because of its restrictiveness - also catches a number of false positives; then a CAPTCHA served as a last resort will allow those real users who get caught to slip by your throttling (thus avoiding annoying DoS situations). The sweet spot, of course, is when ALL the bots get caught in your net, while extremely few real users get bothered by the CAPTCHA. If you, when serving up the 10-minute-old cached pages, also offer an alternative, optional, CAPTCHA-verified 'front page refresher', then humans who really want to keep refreshing, can still do so without getting the old cached page, but at the cost of having to solve a CAPTCHA for each refresh. That is an annoyance, but an optional one just for the die-hard users, who tend to be more forgiving because they know they're gaming the system to improve their chances, and that improved chances don't come free.

第五种方法:诱饵废话:

Christopher Mahan had an idea that I rather liked, but I would put a different spin on it. Every time you are preparing a new offer, prepare two other 'offers' as well, that no human would pick, like a 12mm wingnut for $20. When the offer appears on the front page, put all three 'offers' in the same picture, with numbers corresponding to each offer. When the user/bot actually goes on to order the item, they will have to pick (a radio button) which offer they want, and since most bots would merely be guessing, in two out of three cases, the bots would be buying worthless junk. Naturally, this doesn't address 'alarm bots', and there is a (slim) chance that someone could build a bot that was able to pick the correct item. However, the risk of accidentally buying junk should make scripters turn entirely from the fully automated bots.

第六项措施:僵尸网络节流:

(删除)

Okay............ I've now spent most of my evening thinking about this, trying different approaches.... global delays.... cookie-based tokens.. queued serving... 'stranger throttling'.... And it just doesn't work. It doesn't. I realized the main reason why you hadn't accepted any answer yet was that noone had proposed a way to thwart a distributed/zombie net/botnet attack.... so I really wanted to crack it. I believe I cracked the botnet problem for authentication in a different thread, so I had high hopes for your problem as well. But my approach doesn't translate to this. You only have IPs to go by, and a large enough botnet doesn't reveal itself in any analysis based on IP addresses.

所以你知道了，第六小节是零。没什么。邮政编码。除非僵尸网络很小，或者足够快，可以被通常的IP限制，否则我不认为有任何有效的措施可以对抗僵尸网络，而不涉及明确的人类验证，如CAPTHAs。我很抱歉，但我认为结合以上五种方法是你最好的选择。你可能只需要abelenky的10分钟缓存技巧就可以了。

I think that sandboxing certain IPs is worth looking into. Once an IP has gone over a threshold, when they hit your site, redirect them to a webserver that has a multi-second delay before serving out a file. I've written Linux servers that can handle open 50K connections with hardly any CPU, so it wouldn't be too hard to slow down a very large number of bots. All the server would need to do is hold the connection open for N seconds before acting as a proxy to your regular site. This would still let regular users use the site even if they were really aggressive, just at a slightly degraded experience.

您可以使用这里描述的memcached，以较低的成本跟踪每个IP的命中数。

一个相当简单的解决方案是跟踪呈现表单和获得响应之间的时间差:机器人通常只有极短的毫秒响应时间，没有用户可以做到这一点;或者响应时间极长，长达数小时。

这里有一个django代码片段，以及更详细的描述:

验证码的替代方案(无需人工交互)

让用户在原价和更高的价格之间做出选择。 你必须找到某种方法，将按钮与它们各自的价格联系起来——颜色、位置，也许还有按钮的“情感内涵”——这很难通过编程来确定，但只需要用户将按钮与价格联系起来。 对用户来说简单，直观，没有麻烦，但对脚本编写人员来说困难，更重要的是，有风险——特别是如果您改变了关联方法。