Abstract: A system is provided to detect email spam. During operation, the system receives an email, extracts a set of keywords from the email body, and constructs a first search query based a keyword extracted from the email body. The system further constructs a second search query based on the keyword in the first query and one additional word which pertains to a known spam word or to the subject of the email. Next, the system receives a first number of hits and a second number of hits in response to the first and second search queries, respectively. The system then determines whether the email is spam based on the first number and the second number. The system can also perform Website filtering using inference detection which is based on search results received in response to search queries formulated with keywords extracted from Websites.

Abstract: One embodiment provides a computer system for detecting associations between a reviewer and an entity under review. During operation, the system estimates a relationship strength between the reviewer and the entity under review, and determines whether the relationship strength between the reviewer and the entity under review exceeds a predetermined threshold.

Abstract: One embodiment of the present invention provides a system for resetting a user's forgotten password. During operation, the system receives a user's request for resetting the user's forgotten password and derives one or more challenges from the user's forgotten password. The system then presents the derived challenges to the user and receives a response from the user to the challenges. The system further compares the user's response to the one or more challenges with the user's forgotten password, thereby facilitating password resetting.

Abstract: One embodiment of the present invention provides a system that detects inferences from documents. During operation, the system receives one or more documents and extracts a first set of knowledge relevant to the documents. The system further formulates one or more queries to one or more reference corpora based on the first set of knowledge. The system then extracts a second set of knowledge from results received in response to the queries. Additionally, the system produces a mapping relationship between at least one document and a piece of the second set of knowledge which is not within the first set of knowledge, the mapping relationship indicating an inference from the documents.

Abstract: One embodiment of the present invention provides a system for authenticating a user. During operation, the system records user behavior history at one or more devices associated with the user. The system then extracts user information associated with a place and/or an activity from the recorded user behavior history. The system further generates one or more challenges based on the extracted user information, thereby facilitating the verification of the user's identity.

Abstract: One embodiment of the present invention provides a system for automatically authenticating a user. During operation, the system receives a user's request for authentication. The system then extracts information associated with the user from user-specific information stored in an enterprise computer. The extracted user information does not explicitly relate to a password. The system further generates one or more challenges based on the extracted user information, and receives the user's response to the challenges. Subsequently, the system compares the user's response to the extracted user information, and authenticates the user.

Abstract: One embodiment provides a system that verifies a user's identity. The system generates a list including a plurality of items and formulates a substantially large set of security questions base on the plurality of items. The number of questions in the set is significantly larger than a subset of security questions presented to the user to reduce the likelihood of the same questions being asked repeatedly. During account creation, the system presents to the user the subset of questions, and receives and stores a response from the user. At least one question in the subset is selected based on user information that is automatically extracted from devices associated with the user. Subsequently, the system receives a request to reset the user's password and presents the subset of questions to the requester. The system determines whether the requester is the user by comparing the requester's response with the stored user response.

Abstract: One embodiment of the present invention provides a system that detects sensitive content in a document. In doing so, the system receives a document, identifies a set of terms in the document that are candidate sensitive terms, and generates a combination of terms based on the identified terms that is associated with a semantic meaning. Next, the system performs searches through a corpus based on the combination of terms and determines hit counts returned for each term in the combination and for the combination. The system then determines whether the combination of terms is sensitive based on the hit count for the combination and the hit counts for the individual terms in the combination, and generates a result that indicates portions of the document which contain sensitive combinations.

Abstract: One embodiment of the present invention provides a method for adjusting security status on a mobile device, the method comprising: collecting security-related contextual information which includes information of nearby mobile devices and/or the geographic location of the intelligent mobile device; evaluating a threat level based on the collected security-related contextual information; invoking a security policy; and adjusting the security status of the mobile device based on the threat level and the security policy.

Abstract: A system for displaying a set of selectable CAPTCHAs produces a first set of CAPTCHAs whose images are based at least partially on an alphanumeric sequence, where a respective CAPTCHA in the first set is associated with a CAPTCHA property. The system also produces a second set of CAPTCHAs whose images are based at least partially on an alphanumeric sequence, where a respective CAPTCHA in the second set is not associated with a CAPTCHA property. Next, the system displays the first and second sets of CAPTCHAs. Finally, the system makes respective CAPTCHAs in the first and second sets of CAPTCHAs selectable, thereby allowing a user to pass a CAPTCHA challenge by distinguishing the first set of CAPTCHAs from the second set of CAPTCHAs without typing the words associated with the images.

Abstract: One embodiment of the present invention provides a system that facilitates filtering outbound content via inference detection. During operation, the system identifies content sent to a first address and extracts keywords from the identified content. The system then issues queries based on these keywords and extracts expected-content keywords from the hits returned in response to the queries. The system then searches the outbound content for occurrences of the expected-content keywords and produces a result which allows a user to determine whether the outbound content is proper. In a further embodiment, the system extracts keywords from a piece of outbound content, and issues queries based on these keywords. The system then extracts keywords from the hits, and present at least one keyword to a user, thereby allowing the user to determine whether the outbound content is proper.

Abstract: A system is provided to detect email spam. During operation, the system receives an email, extracts a set of keywords from the email body, and constructs a first search query based a keyword extracted from the email body. The system further constructs a second search query based on the keyword in the first query and one additional word which pertains to a known spam word or to the subject of the email. Next, the system receives a first number of hits and a second number of hits in response to the first and second search queries, respectively. The system then determines whether the email is spam based on the first number and the second number. The system can also perform Website filtering using inference detection which is based on search results received in response to search queries formulated with keywords extracted from Websites.

Abstract: One embodiment of the present invention provides a system that detects inferences from documents. During operation, the system receives one or more documents and extracts a first set of knowledge relevant to the documents. The system further formulates one or more queries to one or more reference corpora based on the first set of knowledge. The system then extracts a second set of knowledge from results received in response to the queries. Additionally, the system produces a mapping relationship between at least one document and a piece of the second set of knowledge which is not within the first set of knowledge, the mapping relationship indicating an inference from the documents.