?¬‚ ickr.com).
Visited URL Enumeration Countermeasure
Countermeasures for this attack are straightforward. A user can protect herself by
disabling JavaScript with a plug-in such as NoScript (http://noscript.net/) for Firefox.
JavaScript Port Scanner
Popularity: 3
Simplicity: 5
Impact: 6
Risk Rating: 5
JavaScript attack tools do not always focus on attacking the user but can instead use
a compromised user to attack other targets of interest. For example, one particular bit of
Figure 4-5 HistoryThief
Chapter 4: Malicious JavaScript and AJAX 97
malicious JavaScript uses the browser as a tool to portscan the internal network. This is
a significant variation from traditional portscans, because modern networks are virtually
guaranteed to be protected from external portscans by a firewall and use of Network
Address Translation (NAT). Often the reliance on a firewall leads to the internal network
being left unhardened against attack. By using JavaScript to cause a victim??™s browser to
perform the portscan, the scan will be conducted from inside the firewall and will provide
an attacker with otherwise unavailable information.
Originally discussed in research by Jeremiah Grossman and Billy Hoffman, malicious
JavaScript can be used in a number of ways to conduct a portscan of internal machines.
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