SPIDER project proposes a SPIT mitigation architecture, which uses a detection layer consisting of various modules and a decision layer. The VoIP SEAL system uses different stages. After a signaling analysis in the first stage, the suspicious callers are subjected to tests (e.g. Audio-CAPTCHAs) and the callee is asked for feedback in later stages. SymRank adapts of the PageRank algorithm and computes the reputation of subscribers based on both incoming and outgoing calls. Furthermore, outliers in total talk duration and in repetitive and reciprocal calls can be used to detect suspicious callers. SPIT detection can make use of sophisticated machine learning algorithms, including semi-supervised machine learning algorithms. A protocol called performs the detection as soon as the call is established providing the option of automatically hanging up a suspect call. It builds on the notion of clustering whereby calls with similar features are placed in a cluster for SPIT or legitimate calls and human input is used to mark which cluster corresponds to SPIT. Call features include those extracted directly from signaling traffic such as the source and destination addresses, extracted from media traffic, such as proportion of silence, and derived from calls, such as duration and frequency of calls. SPIT detection and mitigation can also be based solely on the caller's audio data. This approach uses audio identification techniques (similar to music identification) to detect calls with identical audio data including certain degradations (e.g., noise and different audio codecs). A robust Acoustic fingerprint (perceptual hashing) is derived from spectral parameters of the audio data and replayed calls are identified by a comparison of fingerprints. A prototype solution has been developed within the VIAT project. Researchers Azad and Morla (2013) conducted a study on detecting spam callers in a much accurate and secure approach. They invented a new scheme to detect spam calls without user interaction and prior reviewing the content of the message. The statistics from the several experiments showed this new system effectively detected spammers calling legitimate users without accessing the private information and user interaction. Implementation of mitigation Little information is available about implementations of SPIT mitigation measures by telephone companies. Some recent smartphone vendors are incorporating notification of possible spam for incoming calls, such as Google in its Nexus Android devices and Apple in its iOS 10 release. SPIT is generally not yet considered to be a problem as critical as email spam. An automated analysis