Do antivirus companies distribute virus , malware , spyware etc.?

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It is frequently alleged that the antivirus compaies themselves distribute virus , amlwares , spyware , trojan etc. It is said that this increase the demand for their antivirus softwares . But I have doubt about this allegation . Because , all the antivirus companies offer free versions of their products and from my experiences I am quite satisfied with these free versions . I think most of the internet users are satisfied like me with free versions . Then how come this conspiracy blamed on the companies ?