In the knowledge economy, knowledge is a primary resource. The internet is considered a power of its connectivity. It is used in the internet of things (IoT) to connect passive objects to exhibit their smart features. Similarly, the internet of knowledge is described as the connection of knowledge points originally spread over diverse places to represent them with high value. With the enhancement of the internet of knowledge, the knowledge is progressively found at the network level, such as SNSs. Recently, SNSs have been converted into an essential and prominent medium of communication and sharing knowledge. Typically, SNS users are liable for sharing knowledge in the network and are basic key elements in the network structure. The communities that consist of families, group of friends, and acquaintances are the next basic element in the network structure. In SNSs, users can share knowledge by posting links to their favorite webpages, files, photos, and videos. Furthermore, the structure of SNS communities generates a network of credibility and trust [1, 2]. Facebook and Twitter are leading SNSs. According to a report from Statista [3], the total number of Facebook and Twitter users stood at 1,968 million and 319 million, respectively, as of April 2017. With the escalating number of users, a huge amount of heterogeneous knowledge is also being produced every day on these two SNSs [4]. Mainly, multimedia knowledge (in the form of text, audio files, videos, and images) is produced, stored, and transferred in a huge amount. The multimedia knowledge posted on these SNSs is mostly accompanied by user likes, comments, tags, hashtags, and so on. Multimedia has become an essential part of SNSs. According to Zephoria Digital Marketing’s report [5], approximately 136,000 photos are shared, 293,000 statuses are updated, and 510,000 comments are posted every 60 seconds on Facebook. This report also reveals that the average content sharing rate on Facebook was 4.75 billion pieces of content per day as of May 2013, which was 94% more than the content sharing rate as of August 2012. The Statista report [6] states that Facebook and Twitter play a significant role in global content sharing activities, and that 57% and 18% of social content sharing activities occurred via Facebook and Twitter, respectively, as of the second quarter of 2016. The statistics above and our survey on SNS security [7] demonstrate that the amount of multimedia knowledge shared on Facebook and Twitter is increasing every single day. With this increase in multimedia, however, these two SNSs have become the desired target of spammers for spreading spam. A statistic from Nexgate’s report showed an estimated 355% escalation in social media spam during the first half of 2013 [8].