1. Email networks and the spread of computer viruses Authors:M. E. J. Newman, S. Forrest, and J. Balthrop. Published:September 10, 2002 - Physical Review E 66 Presenter:Jonathan Hendricker

2. Contributions Realization of social network of personal connections through a directed network Provides data about the spread of viruses within social community More effective way in combating infection through strategic targeting Applicable to other socially dependant electronic services

3. Outline The social network – new ground & unique threat Using a real social network – demographic, testing & results Experiment Analysis & Prevention techniques: Random vs. Targeted vaccination

4. Social Network This network is entirely distinct from the physical network of optical fibers and other connections over which data are transferred between computers Social Network of personal not literal connections to users and computers Computers do not have to be linked via network, only via personal connections, i.e. Address Books

5. The PRIMARY vehicle for computer virus transmission is electronic mail. Viruses are distributed via e-mail attachments and are further propagated through the virus using the user’s Address Book for further targets. Address Books provide a unique social network of associations not dependant on physical location Unique Threat

6. Testing of Actual Network 20 Different Types of Address Books Network of 27,841 total users Reduced to16,881 active accounts Any connections from outside the network were omitted though recognized as the viral catalysist

7. Directed Social Network Account B Account C Account A

8. Testing & Results Number of vertices 16881 Number with address books 4581 Number with nonzero in- or out-degrees 10110 Mean number of entries per address book 12.45 Mean degree z ~either in or out! 3.38

9. Testing & Results (cont) Total number of edges 57029 Number of edges that point both ways 13176 Fraction pointing both ways ~reciprocity! 0.231

10. Social in & out-degree sampling Results suggest a semi-directed social network

11. Spread of infection over an email network Pessimistic assumption: virus spread efficiency is 100%  No Anti-virus software or other precautions – Worst Case Scenario Virus spread is directed through Address Book

12. Who’s at risk? The users at the highest level of risk are the those in the “strongly connected component” and the “links-out”(out-degree) Large scale virus infection occurs when there is an infection in the strongly connected component This tells us that this area is of the most importance for virus protection

13. Random vs. Targeted Current virus protection strategies focus on random “vaccination” Ineffective in combating infection, only reduces 10%

14. Weaknesses Only one network analyzed Assumption of no anti-virus protection for network too drastic Statistical equations thrown in with out much explanation Did not discuss privacy issues or vulnerabilities for determining “Strongly Connected Component” Alluded to future use but no examples given