Security and Intercom

Besides having a full time or part time doorman present, you can look into the following options from cheapest to most expensive:

Educating tenants/shareholders about security; do not open the door for random people and to make sure the building door closes fully before leaving the lobby/building; don't buzz in random strangers, etc.
If you have a super, having him clean and attend the lobby every few hours to insure the lobby is clean/safe
Making sure the lobby is very well lit, if it isn't adding lighting or brighter bulbs
Putting signage visible from the front of the building about security cameras monitoring the premises
Adding security cameras if you don't have them already
Adding a dual lobby internal door that is also locked and requires a second buzz in or a key to unlock
Adding a virtual doorman

This was very helpful! Would you consider a video intercom system like the ButterflyMX as worthy of the investment?

We have sent notices around several times, the lobby is well lit and we have cameras although more warnings would be handy.