The data war between companies that have refused to do business with Wikileaks and the online activists keen to defend it is getting more intense.
The tool through which attacks are carried out against websites perceived to be anti-Wikileaks has now been downloaded more than 31,000 times.
Security experts warned people to avoid joining the voluntary botnet.
Targets of the loose-knit group Anonymous have so far included Visa, Mastercard and Paypal.
Amazon is expected to be among firms targeted next using the Anonymous attack tool known as LOIC. When a person installs the tool on their PC it enrols the machine into a voluntary botnet which then bombards target sites with data.