A System for Anonymizing Temporal Phrases of Message Posted in Online Social Networks and for Detecting Disclosure

Time-related information in message posted on-line is one type of sensitive information targeted by attackers, one reason that sharing information online can be risky. Therefore, time information should be anonymized before it is posted in online social networks (OSNs). One approach to reducing the risk is to anonymize the personal information by removing temporal phrases, but this makes the anonymous message loses too much information. We have proposed a system for creating anonymous fingerprints about temporal phrases to cover most of potential cases of OSN disclosure. The fingerprints not only anonymize time-related information but also can be used to identify a person who has disclosed information about the user. In experiment with 16,647 different temporal phrases extracted from about 16 million tweets, the average number of fingerprints created for an OSN message is 526.05 fingerprints. This is significantly better than the 409.58 fingerprints of the state-of-the-art previous detection temporal phrases algorithm. Fingerprints are quantified using a modified normalized certainty penalty metric to ensure that an appropriate level of information anonymity is used for each user´s friend. The algorithm works well not only for temporal phrases in message posted on social networks but also for other types of phrases (such as location and objective ones) or other areas (religion, politics, military, etc.).