As per Flickr Policy, in your 'Privacy Settings', you can choose to make your photos default to the public for anyone to access, restrict access to a limited number of other Flickr users, or keep those photos private so only you can access them. If you do not change your settings, your photos will be public by default. On each photo page, you will also find more granular controls to change each photo settings.
If a photo is publicly visible on the site, anyone who can see the image can find ways to download it. In order to prevent it, you can adjust the privacy settings for your Flickr account so that only people you have designated as â€œfriendsâ€ and â€œfamilyâ€ can see your pictures posted there.
To adjust Flickr Privacy settings