now the defense department is warning u.s. military personnel not to use them, a memo co-signed by the top pentagon intelligence official says the kits could expose personal and genetic information and potentially create unintended security consequences and risk. the kits are hugely popular with over 26 million people having submitted their dna to trace their lineage. privacy concerns have grown along with their populari popularity, given how revealing dna can be. >> one of the things about dna is it's almost always unique so therefore, while you can change your i.d., you can change your password, it's really difficult to change your dna. >> reporter: ancestry.com says it does not share dna data with insurance companies or employers. 23andme says its customers choose how their information will be used and shared though both acknowledge that federal agents and local police can get access to the data with a subpoena or court order. consumer advocates say these kits can help people manage their health and learn their genealogy.