Nearly 58 percent of online users deleted the small files, which are deposited on computers to track Web site habits, the research firm's 2004 survey found. As many as 39 percent may be deleting cookies from their primary computer every month, according to the study, released on Monday.
The market researcher attributes the trend to heightened concern over privacy and security issues among Internet users. Many people are using anti-spyware and firewall applications, it said.
"Many of these applications block third-party cookies by default, and many more will regularly delete cookies from consumers' computers," the report stated.
According to a consumer survey quoted by Jupiter Research, 38 percent said they consider cookies invasive of their security and privacy. Lawmakers and consumer lobbies have been considering the impact of cookies, and network security company Netcraft on Monday pointed out the risks to personal information posed by the theft of cookies by attackers using cross-scripting flaws.
For online businesses, the trend means that cookies may not be an accurate method of tracking regular visitors to their Web sites. If users block cookies, accurate measurement is compromised and higher numbers may be categorized as anonymous, the study said.
"Given the number of sites and applications that depend heavily on cookies for accuracy and functionality, the lack of this data represents (a) significant risk for many companies," analyst Eric Peterson said in a statement. "Because personalization, tracking and targeting solutions require cookies to identify Web visitors over multiple sessions, the accuracy of these solutions has become highly suspect, especially over longer periods of time."