Random IP connected to UMS, possible to block it?

[MasterDMFour]

So I''ve been getting a random IP connecting to my UMS with an "unknown renderer" and have no clue what it is at all as it is not connected to my router in any way as I've gone through and checked them all (ip is) which is not present on any of my devices as they all start with 192.168.x.xxx... Is there any way I can block this specific IP from connecting?

[boss]

Is your ISP BT.

That IP is an IP belonging to an ISP. It could be your external IP form your ISP.
whois 81.148.225.109
% This is the RIPE Database query service.
% The objects are in RPSL format.
%
% The RIPE Database is subject to Terms and Conditions.
% See http://www.ripe.net/db/support/db-terms-conditions.pdf

% Note: this output has been filtered.
% To receive output for a database update, use the "-B" flag.

% Information related to '81.148.224.0 - 81.148.255.255'

% Abuse contact for '81.148.224.0 - 81.148.255.255' is '[email protected]'

inetnum: 81.148.224.0 - 81.148.255.255
remarks: *******************************************************************
remarks: * Report abuse via: http://bt.custhelp.com/app/contact/c/346,3024 *
remarks: *******************************************************************
netname: BT-CENTRAL-PLUS
descr: IP pools
country: GB
admin-c: BTCP1-RIPE
tech-c: BTCP1-RIPE
status: ASSIGNED PA
remarks: Report abuse via: http://bt.custhelp.com/app/contact/c/346,3024
mnt-by: BTNET-MNT
mnt-lower: BTNET-MNT
mnt-routes: BTNET-MNT
created: 2008-12-03T14:06:05Z
last-modified: 2011-02-24T14:40:03Z
source: RIPE

role: BT CENTRAL PLUS - OPERATIONAL SUPPORT
remarks: *******************************************************************
remarks: * Report abuse via: http://bt.custhelp.com/app/contact/c/346,3024 *
remarks: *******************************************************************
address: BT
address: Wholesale
address: UK
abuse-mailbox: [email protected]
admin-c: PC487-RIPE
tech-c: SR401-RIPE
nic-hdl: BTCP1-RIPE
mnt-by: BTNET-MNT
created: 2004-06-08T09:02:16Z
last-modified: 2011-02-21T13:40:11Z
source: RIPE # Filtered

% Information related to '81.128.0.0/11AS2856'

route: 81.128.0.0/11
descr: BT Public Internet Service
origin: AS2856
mnt-by: BTNET-INFRA-MNT
created: 2002-10-22T13:45:17Z
last-modified: 2014-07-31T07:51:30Z
source: RIPE # Filtered

% This query was served by the RIPE Database Query Service version 1.92.6 (WAGYU)

[Nadahar]

You should check your router configuration. Public IPs, like 81.148.225.109, should not have access to your local (192.168.x.x) network.

There is an IP filter in UMS you can use to block specific IPs, but in this case you should rather figure out why your router isn't blocking outside traffic like it's supposed to.