If you purchased one of the DNA packages available out there (Ancestry, Helix, 23andMe), you consented to allow them to share your DNA with other companies. Your information would be anonymized and likely used just for research. However hacks against corporations do occur, as we’ve seen often in the news, and occasionally privacy is violated.
These companies can hold onto your DNA from a decade to indefinitely. Unless you tell them otherwise.
To opt out of the consent to share your DNA, or to even have them discard your DNA entirely, check out the article below for instructions: