Abstract: A technique for distinguishing between a human user and a software robot. The technique includes: receiving a first communication from a device different from the at least one computer; identifying, from the first communication, a request to access a web resource; generating a shuffled image that encodes a challenge text, the generating comprising: generating an initial image encoding the challenge text; dividing the initial image into image portions; and generating the shuffled image as a shuffled arrangement of the image portions; generating decoding information for revealing the challenge text encoded in the shuffled image; transmitting the shuffled image and the decoding information to the device; receiving a second communication from the device; identifying, from the second communication, a response text; and providing the device with access to the web resource based on a comparison between the challenge text and the response text.

Abstract: Techniques for detecting application program spoofing. The techniques include: receiving a communication from an application program executing on a client device different from the at least one computer; identifying from the communication an asserted identity of the application program; and verifying the asserted identity of the application program at least in part by: interacting with the client device to obtain additional information about the application program, and determining whether the additional information about the application program is consistent with the asserted identity of the application program.

Abstract: A technique for distinguishing between a human user and a software robot. The technique includes: receiving a first communication from a device different from the at least one computer; identifying, from the first communication, a request to access a web resource; generating a shuffled image that encodes a challenge text, the generating comprising: generating an initial image encoding the challenge text; dividing the initial image into image portions; and generating the shuffled image as a shuffled arrangement of the image portions; generating decoding information for revealing the challenge text encoded in the shuffled image; transmitting the shuffled image and the decoding information to the device; receiving a second communication from the device; identifying, from the second communication, a response text; and providing the device with access to the web resource based on a comparison between the challenge text and the response text.

Abstract: A technique for distinguishing between a human user and a software robot. The technique includes: receiving a first communication from a device different from the at least one computer; identifying, from the first communication, a request to access a web resource; transmitting software code and location information to the device, wherein the location information specifies a plurality of locations encoding a visual representation of a challenge text, and wherein the software code, when executed by an Internet browser, causes a plurality of graphical elements to be displayed at the plurality of locations in a webpage so that the webpage displays the challenge text; receiving a second communication from the device; identifying, from the second communication, a response text; and providing the device with access to the web resource based on a comparison between the challenge text and the response text.

Abstract: A technique for distinguishing between a human user and a software robot. The technique includes: receiving a first communication from a device different from the at least one computer; identifying, from the first communication, a request to access a web resource; generating an image that encodes a challenge text, the image comprising data stored in a plurality of channels including a transparency channel, the generating comprising: generating decoding information representing the challenge text; and storing the decoding information in the transparency channel of the image; transmitting, via the at least one network, the generated image to the device; receiving a second communication from the device; identifying, from the second communication, a response text; and providing the device with access to the web resource based on a comparison between the challenge text and the response text.

Abstract: Techniques for detecting device type spoofing. The techniques include: receiving a communication from a client device different from the at least one computer; identifying from the communication an asserted type of the client device; and verifying the asserted type of the client device at least in part by: interacting with the client device to obtain additional information about the client device, and determining whether the additional information about the client device is consistent with the asserted type of the client device.