How to find out which apps are creating *.space files in Internal Storage? There is a folder at internal memory:  .space/

Inside it has one folder that is a big hash name (probably sha1sum), and inside that folder there are lots of files (also named as a hash something like 60b725f10c9c85c70d97880dfe8191b3.space) occupying 2.7GB of my smartphone precious internal memory.

In hexa/chars/bytes, thru X-Plore File Manager, I saw that they begin with "PK", which means they are ZIP files. So, after renaming them to .ZIP, I saw many pictures inside them that were all about games, and the manifest.xml was Uber annoying to try to read.

My conclusion, they were all unwanted, unasked, auto-downloaded .ZIP (.APK?) games.

Now I need to stop  the app doing that kind of thing on my precious cellphone's memory.
It looks like a malicious or spamming app. Did you download any app from a suspicious looking website in a date close to the date the .space files were created/modified, as mentioned in the explorer app? Then that downloaded app could be the culprit.

It is not usually possible to directly check what app downloads a specific file, but you can try checking Data Usage and look for apps using suspiciously large bandwidth amounts.

The location of the Data Usage statistics is sometimes different depending on the device and the Android version, but you can usually find the statistics in Settings &gt; Wireless &amp; Networks &gt; Data Usage. If you can't find it there you can try typing "Data Usage" in the settings search box. You can choose to show Wi-Fi usage from the menu button on top right corner, and then you can look for any suspicious apps using large amounts of bandwidth and uninstall them.