Password is not required upon returning from suspend

[Andrey Gelman]

Following the security settings (in Ubuntu System Settings) my system should require password upon waking from suspend or simply returning from a blank screen.
Once it worked this very way, but starting a few months back (unfortunately, I cannot point exactly that moment) it stopped. The computer would seamlessly wake up from a suspend / a blank screen not requiring the password.
I have two 16.04 systems (with quite different hardware specifications) - one suspends when inactive, the other one goes to the blank screen. Both suffer this scenario.
Probably there is some 3-rd party application that causes such behavior ?

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: unity 7.4.0+16.04.20160906-0ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-59.80-generic 4.4.35
Uname: Linux 4.4.0-59-generic x86_64
.tmp.unity_support_test.0:

ApportVersion: 2.20.1-0ubuntu2.5
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: compiz
CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0'
CompositorUnredirectFSW: true
CurrentDesktop: Unity
Date: Tue Jan 31 13:03:49 2017
DistUpgraded: Fresh install
DistroCodename: xenial
DistroVariant: ubuntu
GraphicsCard:
 Intel Corporation Haswell-ULT Integrated Graphics Controller [8086:0a16] (rev 0b) (prog-if 00 [VGA controller])
   Subsystem: Intel Corporation Haswell-ULT Integrated Graphics Controller [8086:2010]
InstallationDate: Installed on 2016-04-28 (278 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
MachineType: CompuLab Ltd. Intense-PC2 (IPC2)
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-59-generic root=UUID=785246f9-2baf-496e-85b9-370033d39a56 ro quiet splash vt.handoff=7
SourcePackage: unity
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 08/29/2014
dmi.bios.vendor: Compulab Ltd.
dmi.bios.version: IPC2_3.330.2 X64
dmi.board.name: Intense-PC2 (IPC2)
dmi.board.vendor: CompuLab Ltd.
dmi.board.version: 1.x
dmi.chassis.type: 9
dmi.chassis.vendor: CompuLab Ltd.
dmi.chassis.version: 0.1
dmi.modalias: dmi:bvnCompulabLtd.:bvrIPC2_3.330.2X64:bd08/29/2014:svnCompuLabLtd.:pnIntense-PC2(IPC2):pvr1.x:rvnCompuLabLtd.:rnIntense-PC2(IPC2):rvr1.x:cvnCompuLabLtd.:ct9:cvr0.1:
dmi.product.name: Intense-PC2 (IPC2)
dmi.product.version: 1.x
dmi.sys.vendor: CompuLab Ltd.
version.compiz: compiz 1:0.9.12.2+16.04.20160823-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.68-1~ppa
version.libgl1-mesa-dri: libgl1-mesa-dri 11.2.0-1ubuntu2.2
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 11.2.0-1ubuntu2.2
version.xserver-xorg-core: xserver-xorg-core 2:1.18.4-0ubuntu0.2
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.10.1-1ubuntu2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.7.0-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20160325-1ubuntu1.2
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.12-1build2
xserver.bootTime: Sun Jan 22 11:58:53 2017
xserver.configfile: default
xserver.errors:

xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:
 product id 41114
 vendor DEL
xserver.version: 2:1.18.4-0ubuntu0.2