The Social Security numbers of 2.5 million dead Americans are used each year by identity thieves, a new study from fraud identity protection firm ID Analytics reports.

According to an article from msnbc.com, this study offers the first hard data about this little-understood aspect of ID theft. ID Analytics worked with credit-granting companies such as banks and cell phone providers to find common patterns amongst fraudsters, noting the Social Security numbers used on 100 million applications filed during the first three months of 2011 and comparing those numbers against the Social Security Administration's Death Master File. The Master File tracks the identities of people after they die, and it currently contains about 40 million SSNs.

Roughly 800,000 deceased Americans are deliberately targeted by criminals each year. These thieves come armed with the deceased person's SSN, name and birthday, and attempt to fully assume the person's identity. 

Meanwhile, SSNs attached to 1.6 million more dead adults find their way onto thieves'  fraudulent applications through random selection, the study says. Criminals just guess at SSNs while filling out applications and accidentally use one that was issued to someone who is now dead. ID Analytics dubs them "identity manipulators" who make arbitrary variations on their own personal information to avoid fraud detection tools. 

"This study brings to light a significant problem, as we see fraudsters intentionally using identities of the deceased at a rate of more than 2,000 per day," says Stephen Coggeshall, chief technology officer at ID Analytics. He says that the imposters have the same goals as any other identity thief – theft of cell phone service or the ability to open up new credit cards or loans.

These frauds are successful because the normal channel for discovery, the consumer noticing unauthorized charges, doesn't exist any more. Family members might discover the fraud through unexpected bills, but recovering from this type of fraud is made more difficult when a third party has to call and ask for corrections, the article says.

Ironically, the article says, if companies don't frequently check SSNs against the Death Master File, it becomes a source for criminals to obtain SSNs to exploit. 

"We have no sense of where criminals are getting the numbers, but a certain portion of them probably are coming from public sources, like the Death Master File," Coggeshall said. 

The study also hinted that seriously ill people are being targeted for identity theft. There were 2 million cases of SSNs' being used in credit applications where the SSN holder died within the next two months. 

Coggeshall recommends that people monitor the credit of their deceased family members for at least a year.