CATPCHA stands for Completely Automated Public Turing Tests to Tell Computers and Humans Apart. A 'Turing Test' is often used in the domain of robotics, to test if a machine possesses artificial intelligence. They are automated versions of the Turing Test. In essence, it refers to the weird, twisted combination of letters and numbers many websites ask you to enter while performing online activities like downloading or financial transactions.
A CAPTCHA is basically a tiny program embedded in the website that aims to identify the user as a human, as opposed to a 'bot' or automated program. It involves presenting a twisted, but readable image of a sequence of letters and/or numbers, which have to be entered in a box provided and submitted to the website. Bots cannot read and decipher letters or numbers from an image, and usually do not manage to 'pass' this test.
First Generation
First generation CAPTCHAs comprised of a simple string of 4 to 6 alphabets. It does not take one long to imagine that cracks for these simple CAPTCHAs emerged quickly. Software were soon coded which could decipher and interpret simple distorted images.
Unbreakable
To build upon the simpler ones, 'Unbreakable' CAPTCHAs were soon invented; these were far more complicated. True to their name, software could not be written to auto-solve these CAPTCHAs. At the same time, they also became a pain for true and legitimate human users, as they were sometimes quite distorted and beyond recognition for humans too!
Are They Really Effective?
Though no software could be written to break 'Unbreakable's", the ingenuity of the hacker's and spammer's brains soon took over. They simply outsourced cracking CAPTCHAs to cheap-labor countries abroad, who sold it back to them at rates low as a couple of bucks for a 1000 solved CAPTACHAs. Beats the very purpose, but still very much within the legal framework.
Alternates to Text CAPTCHAs
- It is now increasingly common to move away from text based CAPTCHAs and instead present either an image which needs to be identified or a simple arithmetic calculation (2+2=?). Another kind of CAPTCHA is identification of basic colors.
- Others include a Flash animation with sound/images, requiring the viewer to identify certain phrases/text contained within. But solving these CAPTCHAs are a pain and spammers could easily get hold of solved CAPTACHAs for a meagre price, and hence they never really became popular.
- Another unique CAPTCHA includes honeypot fields in an online form - fields that are invisible to humans, but not to bots. If these fields get filled, it's probably the work of bots and not humans.
- Gmail has another unique CAPTCHA, which makes human intervention essential. It associates account activation with a short activation code sent to a mobile phone by SMS. This code then needs to be entered to activate the account. This is quite an effective method to prevent bulk creation of spam accounts by bots.
The Net is basically a battlefield between spammers and hackers versus legitimate users and companies. More and more unique ways to fight them will need to be devised to stay safe in this cyber-world.
Jitesh Iyer - Hi! I'm Dr. Jitesh Iyer, from India. I've completed my Masters in Pharmaceutical Sciences and PhD in Biotechnology and Cell Biology. I'm a ...
