How did unidentified photo appear in my album

I found a mystery photo in my iPod touch photo album this morning. I definitely did not take it myself. (It looked like a retake of a b/w photo of middle eastern "soldiers" holding a flag.)

I have deleted it but am concerned as to whether my device might have some sort of malware.... and want to know if there are steps I should take.

I am usually careful to delete cookies, data, history etc Since the device is old, the OS is also old, but updated to its limit.

i am guessing that the picture was downloaded when I accidentally hit an ad when scrolling through news articles.