Site to Site VPN - security of the device at the DR site

Hi, we have a site to site VPN from a Sonicwall NSA 2600 on our main site, to a Sonicwall TZ 105 on our DR site which stores our backups.

The NSA 2600 has the license for sonicwall advanced gateway security suite which has intrusion protection.

The Sonicwall TZ 105 doesn't have a license for any suite, but it doesn't have any ports open or any external access.

I wondered from a security point of view should it have some license for a security suite? 

So that hackers couldnt hack into the Sonicwall TZ 105 from the outside?

Thanks!