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The popularity of Twitter has attracted spammers to disseminate large amount of spam messages. Preliminary studies had shown that most spam messages were produced automatically by bot. Therefore bot spammer detection can reduce the number of spam messages in Twitter significantly. However, to the best of our knowledge, few researches have focused in detecting Twitter bot spammer. Thus, this paper proposes a novel approach to differentiate between bot spammer and legitimate user accounts using time interval entropy and tweet similarity. Timestamp collections are utilized to calculate the time interval entropy of each user. Uni-gram matching-based similarity will be used to calculate tweet similarity. Datasets are crawled from Twitter containing both normal and spammer accounts. Experimental results showed that legitimate user may exhibit regular behavior in posting tweet as bot spammer. Several legitimate users are also detected to post similar tweets. Therefore it is less optimal to detect bot spammer using one of those features only. However, combination of both features gives better classification result. Precision, recall, and f-measure of the proposed method reached 85,71%, 94,74% and 90% respectively. It outperforms precision, recall, and f-measure of method which only uses either time interval entropy or tweet similarity.

Ant Colony Optimization (ACO) is a nature-inspired optimization algorithm which is motivated by ants foraging behavior. Due to its favorable advantages, ACO has been widely used to solve several NP-hard problems, including edge detection. Since ACO initially distributes ants at random, it may cause imbalance ant distribution which later affects path discovery process. In this paper an adaptive ACO is proposed to optimize edge detection by adaptively distributing ant according to gradient analysis. Ants are adaptively distributed according to gradient ratio of each image regions. Region which has bigger gradient ratio, will have bigger number of ant distribution. Experiments are conducted using images from various datasets. Precision and recall are used to quantitatively evaluate performance of the proposed algorithm. Precision and recall of adaptive ACO reaches 76.98 % and 96.8 %. Whereas highest precision and recall for standard ACO are 69.74 % and 74.85 %. Experimental results show that the adaptive ACO outperforms standard ACO which randomly distributes ants.

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