Webbots, Spiders, & Screen Scrapers

Description

The Internet is bigger and better than what a mere browser allows. Webbots, Spiders, and Screen Scrapers is for programmers and businesspeople who want to take full advantage of the vast resources available on the Web. There's no reason to let browsers limit your online experience-especially when you can easily automate online tasks to suit your individual needs. Learn how to write webbots and spiders that do all this and more: Programmatically download entire websites Effectively parse data from web pages Manage cookies Decode encrypted files Automate form submissions Send and receive email Send SMS alerts to your cell phone Unlock password-protected websites Automatically bid in online auctions Exchange data with FTP and NNTP servers Sample projects using standard code libraries reinforce these new skills. You'll learn how to create your own webbots and spiders that track online prices, aggregate different data sources into a single web page, and archive the online data you just can't live without. You'll learn inside information from an experienced webbot developer on how and when to write stealthy webbots that mimic human behavior, tips for developing fault-tolerant designs, and various methods for launching and scheduling webbots. You'll also get advice on how to write webbots and spiders that respect website owner property rights, plus techniques for shielding websites from unwanted robots. As a bonus, visit the author's website to test your webbots on sample target pages, and to download the scripts and code libraries used in the book. Some tasks are just too tedious-or too important!- to leave to humans. Once you've automated your online life, you'll never let a browser limit the way you use the Internet again. Acknowledgments Tables of Contents Introduction Old-School Client-Server Technology The Problem with Browsers What to Expect from This Book Learn from My Mistakes Master Webbot Techniques Leverage Existing Scripts About the Website About the Code Requirements Hardware Software Internet Access A Disclaimer (This Is Important) PART I: Fundamental Concepts and Techniques 1: What’s in It for You? Uncovering the Internet’s True Potential What’s in It for Developers? Webbot Developers Are in Demand Webbots Are Fun to Write Webbots Facilitate “Constructive Hacking” What’s in It for Business Leaders? Customize the Internet for Your Business Capitalize on the Public’s Inexperience with Webbots Accomplish a Lot with a Small Investment Final Thoughts 2: Ideas for Webbot Projects Inspiration from Browser Limitations Webbots That Aggregate and Filter Information for Relevance Webbots That Interpret What They Find Online Webbots That Act on Your Behalf A Few Crazy Ideas to Get You Started Help Out a Busy Executive Save Money by Automating Tasks Protect Intellectual Property Monitor Opportunities Verify Access Rights on a Website Create an Online Clipping Service Plot Unauthorized Wi-Fi Networks Track Web Technologies Allow Incompatible Systems to Communicate Final Thoughts 3: Downloading Web Pages Think About Files, Not Web Pages Downloading Files with PHP’s Built-in Functions Downloading Files with fopen() and fgets() Downloading Files with file() Introducing PHP/CURL Multiple Transfer Protocols Form Submission Basic Authentication Cookies Redirection Agent Name Spoofing Referer Management Socket Management Installing PHP/CURL LIB_http Familiarizing Yourself with the Default Values Using LIB_http Learning More About HTTP Headers Examining LIB_http’s Source Code Final Thoughts 4: Parsing Techniques Parsing Poorly Written HTML Standard Parse Routines Using LIB_parse Splitting a String at a Delimiter: split_string() Parsing Text Between Delimiters: return_between() Parsing a Data Set into an Array: parse_array() Parsing Attribute Values: get_attribute() Removing Unwanted Text: remove() Useful PHP Functions Detecting Whether a String Is Within Another String Replacing a Portion of a String with Another String Parsing Unformatted Text Measuring the Similarity of Strings Final Thoughts Don’t Trust a Poorly Coded Web Page Parse in Small Steps Don’t Render Parsed Text While Debugging Use Regular Expressions Sparingly 5: Automating Form Submission Reverse Engineering Form Interfaces Form Handlers, Data Fields, Methods, and Event Triggers Form Handlers Data Fields Methods Event Triggers Unpredictable Forms JavaScript Can Change a Form Just Before Submission Form HTML Is Often Unreadable by Humans Cookies Aren’t Included in the Form, but Can Affect Operation Analyzing a Form Final Thoughts Don’t Blow Your Cover Correctly Emulate Browsers Avoid Form Errors 6: Managing Large Amounts of Data Organizing Data Naming Conventions Storing Data in Structured Files Storing Text in a Database Storing Images in a Database Database or File? Making Data Smaller Storing References to Image Files Compressing Data Removing Formatting Thumbnailing Images Final Thoughts PART II: Projects 7: Price-Monitoring Webbots The Target Designing the Parsing Script Initialization and Downloading the Target Further Exploration 8: Image-Capturing Webbots Example Image-Capturing Webbot Creating the Image-Capturing Webbot Binary-Safe Download Routine Directory Structure The Main Script Further Exploration Final Thoughts 9: Link-Verification Webbots Creating the Link-Verification Webbot Initializing the Webbot and Downloading the Target Setting the Page Base Parsing the Links Running a Verification Loop Generating Fully Resolved URLs Downloading the Linked Page Displaying the Page Status Running the Webbot LIB_http_codes LIB_resolve_addresses Further Exploration 10: Anonymous Browsing Webbots Anonymity with Proxies Non-proxied Environments Your Online Exposure Proxied Environments The Anonymizer Project Writing the Anonymizer Final Thoughts 11: Search-Ranking Webbots Description of a Search Result Page What the Search-Ranking Webbot Does Running the Search-Ranking Webbot How the Search-Ranking Webbot Works The Search-Ranking Webbot Script Initializing Variables Starting the Loop Fetching the Search Results Parsing the Search Results Final Thoughts Be Kind to Your Sources Search Sites May Treat Webbots Differently Than Browsers Spidering Search Engines Is a Bad Idea Familiarize Yourself with the Google API Further Exploration 12: Aggregation Webbots Choosing Data Sources for Webbots Example Aggregation Webbot Familiarizing Yourself with RSS Feeds Writing the Aggregation Webbot Adding Filtering to Your Aggregation Webbot Further Exploration 13: FTP Webbots Example FTP Webbot PHP and FTP Further Exploration 14: NNTP News Webbots NNTP Use and History Webbots and Newsgroups Identifying News Servers Identifying Newsgroups Finding Articles in Newsgroups Reading an Article from a Newsgroup Further Exploration 15: Webbots That Read Email The POP3 Protocol Logging into a POP3 Mail Server Reading Mail from a POP3 Mail Server Executing POP3 Commands with a Webbot Further Exploration Email-Controlled Webbots Email Interfaces 16: Webbots That Send Email Email, Webbots, and Spam Sending Mail with SMTP and PHP Configuring PHP to Send Mail Sending an Email with mail() Writing a Webbot That Sends Email Notifications Keeping Legitimate Mail out of Spam Filters Sending HTML-Formatted Email Further Exploration Using Returned Emails to Prune Access Lists Using Email as Notification That Your Webbot Ran Leveraging Wireless Technologies Writing Webbots That Send Text Messages 17: Converting a Website into a Function Writing a Function Interface Defining the Interface Analyzing the Target Web Page Using describe_zipcode() Final Thoughts Distributing Resources Using Standard Interfaces Designing a Custom Lightweight “Web Service” PART III: Advanced Technical Considerations 18: Spiders How Spiders Work Example Spider LIB_simple_spider harvest_links() archive_links() get_domain() exclude_link() Experimenting with the Spider Adding the Payload Further Exploration Save Links in a Database Separate the Harvest and Payload Distribute Tasks Across Multiple Computers Regulate Page Requests 19: Procurement Webbots and Snipers Procurement Webbot Theory Get Purchase Criteria Authenticate Buyer Verify Item Evaluate Purchase Triggers Make Purchase Evaluate Results Sniper Theory Get Purchase Criteria Authenticate Buyer Verify Item Synchronize Clocks Time to Bid? Submit Bid Evaluate Results Testing Your Own Webbots and Snipers Further Exploration Final Thoughts 20: Webbots and Cryptography Designing Webbots That Use Encryption SSL and PHP Built-in Functions Encryption and PHP/CURL A Quick Overview of Web Encryption Local Certificates Final Thoughts 21: Authentication What Is Authentication? Types of Online Authentication Strengthening Authentication by Combining Techniques Authentication and Webbots Example Scripts and Practice Pages Basic Authentication Session Authentication Authentication with Cookie Sessions Authentication with Query Sessions Final Thoughts 22: Advanced Cookie Management How Cookies Work PHP/CURL and Cookies How Cookies Challenge Webbot Design Purging Temporary Cookies Managing Multiple Users’ Cookies Further Exploration 23: Scheduling Webbots and Spiders The Windows Task Scheduler Preparing Your Webbots to Run as Scheduled Tasks Scheduling a Webbot to Run Daily Complex Schedules Non-Calendar-Based Triggers Final Thoughts Determine the Webbot’s Best Periodicity Avoid Single Points of Failure Add Variety to Your Schedule PART IV: Larger Considerations 24: Designing Stealthy Webbots and Spiders Why Design a Stealthy Webbot? Log Files Log-Monitoring Software Stealth Means Simulating Human Patterns Be Kind to Your Resources Run Your Webbot During Busy Hours Don’t Run Your Webbot at the Same Time Each Day Don’t Run Your Webbot on Holidays and Weekends Use Random, Intra-fetch Delays Final Thoughts 25: Writing Fault-Tolerant Webbots Types of Webbot Fault Tolerance Adapting to Changes in URLs Adapting to Changes in Page Content Adapting to Changes in Forms Adapting to Changes in Cookie Management Adapting to Network Outages and Network Congestion Error Handlers 26: Designing Webbot-Friendly Websites Optimizing Web Pages for Search Engine Spiders Well-Defined Links Google Bombs and Spam Indexing Title Tags Meta Tags Header Tags Image alt Attributes Web Design Techniques That Hinder Search Engine Spiders JavaScript Non-ASCII Content Designing Data-Only Interfaces XML Lightweight Data Exchange SOAP 27: Killing Spiders Asking Nicely Create a Terms of Service Agreement Use the robots.txt File Use the Robots Meta Tag Building Speed Bumps Selectively Allow Access to Specific Web Agents Use Obfuscation Use Cookies, Encryption, JavaScript, and Redirection Authenticate Users Update Your Site Often Embed Text in Other Media Setting Traps Create a Spider Trap Fun Things to Do with Unwanted Spiders Final Thoughts 28: Keeping Webbots out of Trouble It’s All About Respect Copyright Do Consult Resources Don’t Be an Armchair Lawyer Trespass to Chattels Internet Law Final Thoughts A: PHP/CURL Reference Creating a Minimal PHP/CURL Session Initiating PHP/CURL Sessions Setting PHP/CURL Options CURLOPT_URL CURLOPT_RETURNTRANSFER CURLOPT_REFERER CURLOPT_FOLLOWLOCATION and CURLOPT_MAXREDIRS CURLOPT_USERAGENT CURLOPT_NOBODY and CURLOPT_HEADER CURLOPT_TIMEOUT CURLOPT_COOKIEFILE and CURLOPT_COOKIEJAR CURLOPT_HTTPHEADER CURLOPT_SSL_VERIFYPEER CURLOPT_USERPWD and CURLOPT_UNRESTRICTED_AUTH CURLOPT_POST and CURLOPT_POSTFIELDS CURLOPT_VERBOSE CURLOPT_PORT Executing the PHP/CURL Command Retrieving PHP/CURL Session Information Viewing PHP/CURL Errors Closing PHP/CURL Sessions B: Status Codes HTTP Codes NNTP Codes C: SMS Email Addresses Index