Image Spam Filters Based on Optical Character Recognition (OCR) Techniques
Advances in information security, privacy, and ethics book series · 2017
In 2003, the first image with the spam text inside was reported by Graham-Cumming. Later, this technique was utilized successfully by spammers, by sending image spam as MIME attachments instead of sending as simple image tags. The previous content filtering techniques based on text analysis of subject and body fields of email were ineffective to handle this new spam attack type. The first attempts made by researchers to detect such spam were based on Optical Character Recognition (OCR) methods. These methods tried to extract the spam texts/words from image spam and compare with existing spam text keyword database. This chapter provides the details of OCR methods, a literature review on spam filters based on OCR methods and their limitations.