11 A Hybrid Phish Detection Approach by Identity Discovery and Keywords Retrieval Reporter: 林佳宜 /10/17

References Xiang, G., and J.I. Hong. (2009). A Hybrid Phish Detection Approach by Identity Discovery and Keywords Retrieval. In Proceedings of WWW 2009 Full paper 2

3 Outline Introduction Hybrid detect approach System architecture Experimental evaluation Conclusion

Introduction Phishing is a significant security threat to the Internet  causes tremendous economic loss every year Proposed a novel hybrid phish detection method  information extraction (IE) 、 information retrieval (IR) Identity-based component by  directly discovering the inconsistency between their identity and the identity they are imitating. Keywords-retrieval component utilizes  IR algorithms exploiting the power of search engines to identify phish 4

Define phish webpage Satisfying the following criteria ◦ It impersonates well-known websites by replicating the whole or part of the target sites, showing high visual similarity to its targets. ◦ It is associated with a domain usually unrelated to that of its target website. ◦ It has a login form requesting sensitive information. 5

Phishing Site of eBay 6

Exploits a few properties Website brand names usually appear  title, copyright field The domain keyword is the segment in the domain representing the brand name  “Paypal” for “paypal.com Phishing webpages are much less likely to be crawled and indexed by major search engines  short-lived nature  few in-coming links 7

Hybrid approach(1/2) Consists of an  identity-based detection component  keywords-retrieval detection component Requires no  training data,  no prior knowledge of phishing signatures and specific implementations  and thus is able to adapt quickly to the constantly appearing new phishing patterns 8

Hybrid approach(2/2) Relies on identity recognition to  find the domain of the page’s declared identity  examines the legitimacy of the webpage by comparing this extracted domain with its own domain  site:declared brand domain “page domain” Not directly match two domain strings  some closely related domains (e.g., company affiliations)  such as “blogger.com” and “blogspot.com” 9

Named Entity Recognizer The NE identity recognition module augments the retrieval-based one in cases  brand names are absent in title and copyright field to control false positives  an auxiliary module to the identitybased component to reduce false positives Identifies from the  page content  meta keywords/description tags Using the well-known TF-IDF scoring function  get top ranking keywords 10

TF-IDF Algorithm Yield a weight that measures how important a word is to a document in a corpus Term Frequency (TF) ◦ The number of times a given term appears in a specific document ◦ Measure of the importance of the term within the particular document Inverse Document Frequency (IDF) ◦ Measure how common a term is across an entire collection of documents A term has a high TF-IDF weight ◦ A high term frequency in a given document ◦ A low document frequency in the whole collection of documents 11

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Login form detection(1/2) Using the HTML DOM to identify login forms Forms on a page is characterized by three properties  FORM tags  INPUT tags  login keywords such as password 13

Login form detection(2/2) Designed the following algorithm to declare the existence of a login form  form tags, input tags and login keywords all appear in the DOM  Return true if all three are found  form and input tags are found, but login-related keywords exist outside  searching keyword “search”  Return true if a match is found  forms and inputs are detected, but phishers put login keywords in images  phishers put login keywords in images and refrain from using text to avoid being detected  return true if no text is found and only images exist 14

System architecture 15

Two strategies To accurately map a brand name to its domain,define two strategies in selecting domains when domain query matches occur. Strategy I:  evaluate domain-query matches among the top 5 search results of Google and Yahoo  If both search engines have such matches and the domain of the No.1 match from each side coincides  take it as a candidate domain of the brand corresponding to the query  If only one search engine has matches, we take the No.1 domain as a candidate brand domain Strategy II:  Just take the two branches corresponding to the italicized part of strategy I. 16

Data and Usage Our webpage collection consists of phishing cases from one source, and good webpages from six sources Phishing pages  collecting a total of 7906 phishing webpages from Phishtank Good pages came from  Alexa.com  Google: pages with keywords “signin” and “login”  3Sharp  Yahoo :directory’s bank category,Yahoo misc pages  prominent pages 17

Detecting Login Forms Successfully detected 99.82% phishing pages with login forms Remaining 0.18% (14 in absolute number) phishing pages  they either do not have a login form  use login keywords not in our list such as “serial key”  or organize the form/input tags in a way our method misses 18

Identity-based Detection under Strategy I(1/2) Experimented with five approaches, i.e., detection by ◦ title ◦ copyright ◦ TF-IDF ◦ title + copyright + NE ◦ a full-blown method with a combination of the four 19

Identity-based Detection under Strategy I(2/2) All individual detection algorithms have low FP(< 1.5%) 20

Identity-based Detection across Strategies Considering the different sizes of the phish (7906) and legitimate (3543) corpus 21

Evaluation with Other TF-IDF Approaches Zhang et al proposed CANTINA ◦ a content-based method ◦ against two state-of-the-art toolbars, SpoofGuard and Netcraft 22

23 Conclusion Presented the design and evaluation of a hybrid phish detection method Achieved a true positive rate of 90.06% with a false positive rate of 1.95%. Not requiring existing phishing signatures and training data

Questions 24