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Yahoo! Slurp too Stupid to be a Robot

I really hate bad robots. When a web crawler, spider, bot — or whatever you want to call it — behaves in a way that is contrary to expected and/or accepted protocols, we say that the bot is acting suspiciously, behaving badly, or just acting stupid in general. Unfortunately, there are thousands — if not hundreds of thousands — of nefarious bots violating our websites every minute of the day. For the most part, there are effective methods available enabling us to protect our sites against the endless hordes of irrelevant and mischievous bots. Such evil is easily blocked with […] Read more »

Building the Perishable Press 4G Blacklist

Last year, after much research and discussion, I built a concise, lightweight security strategy for Apache-powered websites. Prior to the development of this strategy, I relied on several extensive blacklists to protect my sites against malicious user agents and IP addresses. Unfortunately, these mega-lists eventually became unmanageable and ineffective. As increasing numbers of attacks hit my server, I began developing new techniques for defending against external threats. This work soon culminated in the release of a “next-generation” blacklist that works by targeting common elements of decentralized server attacks. Consisting of a mere 37 lines, this “2G” Blacklist provided enough protection […] Read more »

Controlling Proxy Access with HTAccess

In my recent article on blocking proxy servers, I explain how to use HTAccess to deny site access to a wide range of proxy servers. The method works great, but some readers want to know how to allow access for specific proxy servers while denying access to as many other proxies as possible. Fortunately, the solution is as simple as adding a few lines to my original proxy-blocking method. Specifically, we may allow any requests coming from our whitelist of proxy servers by testing Apache’s HTTP_REFERER variable, like so: RewriteCond %{HTTP_REFERER} !(.*)allowed-proxy-01.domain.tld(.*) RewriteCond %{HTTP_REFERER} !(.*)allowed-proxy-02.domain.tld(.*) RewriteCond %{HTTP_REFERER} !(.*)allowed-proxy-03.domain.tld(.*) Read more »

Better WordPress Archives via Dynamic Triple Column Layout

Here at Perishable Press, the number of posts listed in my archives is rapidly approaching the 700 mark. While this is good news in general, displaying such a large number of posts in an effective, user-friendly fashion continues to prove challenging. Unfortunately, my current strategy of simply dumping all posts into an unordered list just isn’t working. I think it’s fair to say that archive lists containing more than like 50 or 100 post titles are effectively useless and nothing more than a usability nightmare. With growing numbers of blogs building up massive collections of posts, finding better ways to […] Read more »

Eight Ways to Blacklist with Apache’s mod_rewrite

With the imminent release of the next series of (4G) blacklist articles here at Perishable Press, now is the perfect time to examine eight of the most commonly employed blacklisting methods achieved with Apache’s incredible rewrite module, mod_rewrite. In addition to facilitating site security, the techniques presented in this article will improve your understanding of the different rewrite methods available with mod_rewrite. Blacklist via Request Method This first blacklisting method evaluates the client’s request method. Every time a client attempts to connect to your server, it sends a message indicating the type of connection it wishes to make. There are […] Read more »

Unobtrusive JavaScript for ‘Print-This’ Links

One of the oldest JavaScript tricks in the book involves providing a “print this!” link for visitors that enables them to summon their operating system’s default print dialogue box to facilitate quick and easy printing of whatever page they happen to be viewing. With the old way of pulling this little stunt, we write this in the markup comprising the target “print this!” link in question: <a href=”javascript:window.print()”>Print This!</a> Big yuck there, of course, due to the obtrusive nature of the JavaScript implementation. Adhering to the principles of proper Web Standards, it is better practice to separate behavior from structure […] Read more »

Cross-Browser Transparency via CSS

Shortest post ever! You can quickly and easily apply transparency to any supportive element by adding the following CSS code your stylesheet: selector { filter: alpha(opacity=50); /* internet explorer */ -khtml-opacity: 0.5; /* khtml, old safari */ -moz-opacity: 0.5; /* mozilla, netscape */ opacity: 0.5; /* fx, safari, opera */ } Check the code comments to see what’s doing what, and feel free to adjust the level of transparency by editing the various property values. Also, remember to replace “selector” with the target element of your choice. By the way, I’ve got a metric tonne of juicy CSS posts scheduled […] Read more »

PHP and JavaScript Fallbacks for Your Public Feedburner Count

With the recent Feedburner service outage, many sites across the Web experienced severe drops in their Feedburner subscriber counts. Apparently, Google is requiring all Feedburner accounts to be transferred over to Google by the end of February. In the midst of this mass migration, chaotic subscriber data has been reported to include everything from dramatic count drops and fluctuating reach statistics to zero-count values and dreaded “N/A” subscriber-count errors. Obviously, displaying erroneous subscriber-count data on your site is not a good thing. Fortunately, there are several ways to ensure that this doesn’t happen. Over at CSS Newbie, author Rob Glazebrook […] Read more »

Targeting External Links Intelligently

In the beginning… In the time of the dinosaurs, HTML authors controlled the way anchors opened by adding target=”_blank” as an attribute on an anchor tag. Then the molten mass of Internet began to cool into the thin crust of Web 2.0, the continents began to separate and there came a great migration of pages from HTML to the shinier, new XHTML. Most authors didn’t know what that meant, but it had an “X” in it, so it must be cool, they thought. Alas, there came a great despair as the beloved target=”_blank” attribute was no longer looked kindly upon […] Read more »

Better Image Caching with CSS

I have written previously on the fine art of preloading images without JavaScript using only CSS. These caching techniques have evolved in terms of effectiveness and accuracy, but may be improved further to allow for greater cross-browser functionality. In this post, I share a “CSS-only” preloading method that works better under a broader set of conditions. Previous image-preloading techniques target all browsers, devices, and media types. Unfortunately, certain browsers do not load images that are hidden directly (via the <img /> element) or indirectly (e.g., via the parent <div></div> element) using either display:none; or visibility:hidden;. Further problematic is the potential […] Read more »

Temporary PHP Redirect: Allow Multiple IP Access and Redirect Everyone Else

In my previous article on temporarily redirecting visitors during site updates, I present numerous PHP and HTAccess methods for handling traffic during site maintenance, updates, and other temporary periods of downtime. Each of the PHP methods presented in the article allow for access from a single IP while redirecting everyone else. In this article, we modify our previous techniques to allow access for multiple IP addresses while temporarily redirecting everyone else to the page of our choice. Plus, while we’re at it, we’ll explore a few additional ways to adapt and use the general technique. Read more »

PHP Short Open Tag: Convenient Shortcut or Short Changing Security?

Most of us learned how to use “echo()” in one of our very first PHP tutorials. That was certainly the case for me. As a consequence, I never really had a need to visit PHP’s documentation page for echo(). On a recent visit to Perishable Press, I saw a Tumblr post from Jeff about the use of PHP’s shortcut syntax for echo() but somewhere deep in my memory, there lurked a warning about its use. I decided to investigate. Read more »

The Halving Method of Identifying Problematic Code

Working a great deal with blacklists, I am frequently trying to isolate and identify problematic code. For example, a blacklist implementation may suddenly prevent a certain type of page from loading. In order to resolve the issue, the blacklist is immediately removed and tested for the offending directive(s). This situation is common to other coding languages as well, especially when dealing with CSS. Identifying problem code is more of an art form than a science, but fortunately, there are a few ways to improve your overall code-sleuthing strategy. Read more »

New and Improved JavaScript Clock

Earlier this year, I posted an article explaining how to implement an unobtrusive JavaScript dynamic clock. While not completely earth-shattering or cutting-edge or anything like that, the dynamic JavaScript clock has received some great feedback from users who found the script to be exactly what they were looking for. In fact, a couple of weeks ago, Bill Brown went above and beyond by taking the time to improve the script with some great new features, including a “blinking seconds separator (for kicks)” and removal of “the need for the noscript tag.” Here is the complete script sent by Bill in […] Read more »

Redirect All (Broken) Links from any Domain via HTAccess

Here’s the scene: you have been noticing a large number of 404 requests coming from a particular domain. You check it out and realize that the domain in question has a number of misdirected links to your site. The links may resemble legitimate URLs, but because of typographical errors, markup errors, or outdated references, they are broken, leading to nowhere on your site and producing a nice 404 error for every request. Ugh. Or, another painful scenario would be a single broken link on a highly popular site. For example, you may have one of your best posts mentioned in […] Read more »

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