Check out this blank UA visitor.

[born2run]

So I'm seeing a lot of visits from this IP all with blank UAs and from the access-log here is a sample data:

139.162.x.x - - [02/Mar/2018:10:02:39 +0000] "GET /xyzdirectory/ HTTP/1.1" 200 36489 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36"

It's a linode.com host and keyplyr already wrote up the following on this site:
=
"Data-mining software allowing end user to post content to social media. Not clear if this includes a link to source. Also, data for marketers (Adsense, Bing Ads, etc)"
=

What should I do with this? Thanks!

[robzilla]

That looks like a blank referer, not a blank User Agent :-)

[born2run]

Oops right

[TorontoBoy]

Is not the referrer "-"? This is pretty a common referrer.

You should provide the third octet of the IP, as 139.162.x.x does not give me enough meat to comment.

[keyplyr]

Blank referrers are common, especially nowadays with incognito browsing, company firewalls, SEs removing them and secure server configs.

Nothing blatantly suspicious with a blank referrer IMO.

[wilderness]

Major Search Engines have been basically using blank refers (although technically not) for more than decade, and since they converted to encrypted refers.

[born2run]

Yes I've not blocked blank referrers thanks for pointing this out..