First you need to decide if your VM connected to your host machine via a bridge connection or via a NAT, but ether way you’ll need to put the VM IP address in putty to be able to connect to ip, in the VM terminal run this command to show you the machine IP address
(and no 127.0.0.1 is not the machine IP address)

VM # ip addr show

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 52:54:00:d9:16:b3 brd ff:ff:ff:ff:ff:ff
    inet 10.0.2.15/24 brd 10.0.2.1 scope global eth0
       valid_lft forever preferred_lft forever

in this case my IP address will by 10.0.2.15,

First try to make sure you can communicate on a basic level with VM, open a terminal window on your host, and try to ping the VM

HOST # ping 10.0.2.15

PING 10.0.2.15 (10.0.2.15) 56(84) bytes of data.
64 bytes from 10.0.2.15: icmp_seq=1 ttl=64 time=0.045 ms
64 bytes from 10.0.2.15: icmp_seq=2 ttl=64 time=0.110 ms
64 bytes from 10.0.2.15: icmp_seq=3 ttl=64 time=0.099 ms

If you get ant result, then make sure you have a ssh service running on the VM, in the terminal on your VM type as root,

VM # netstat -lnpt | grep 22
tcp   0  0  0.0.0.0:22  0.0.0.0:*  LISTEN  2361/sshd

This tell as we have a service/process with PID(2361) called sshd (OpenSSH daemon) listening to port 22.

You can test if the service work correctly by trying to ssh to it from the VM it self,

VM # ssh 127.0.0.1

Next you neet to make sure that you are not blocking port 22 in your firewall/iptables, I can not believe so, but check it out anyway. In the VM type this command to show you the iptables,

VM # iptables -nvL INPUT

in the output you should have line like this one:

0  0  ACCEPT  tcp  --  *  *  0.0.0.0/0  0.0.0.0/0  tcp  dpt:22  ctstate  NEW

I wanted to use putty to connect to my ubuntu on virtual box (comfort reasons, the VB is just weird. I can’t work unless it is on a proper terminal).
Anyway,

1. Make sure ssh client is installed on your Linux. If not, install it sudo apt install ssh.
2. Power off the OS.
3. Now on your VB go to Settings -> Network -> on Adapter 1 choose Host-only adapter->click OK.
4. Now start your OS. Run ifconfig; now the inet address is your IP.
5. Use this and run it on your putty. Login with your credentials.

The only disadvantage of using host-only adapter is that your guest OS won’t have access to the wider network (eg the Internet).

If you also need your VM to have internet access, leave Adapter 1 as NAT and enable Adapter 2, configured as a Host-Only adapter. This will allow your VM to connect to the internet using NAT as well as make a local connection to your Host using Host-Only.

The following instructions worked with Ubuntu 14.04 and Oracle VirtualBox 4.3.30.

Do this in VirtualBox:

1. Right-click your virtual machine, select “Settings”, and then select “Network”.

2. Next to “Attached to”, select “Host-only Adapter”. As a side note, “Bridged Adapter” will also work, check the VirtualBox documentation for more details about each option.

Do this inside your Virtual Machine:

1. Find your network IP address by opening a terminal and typing ifconfig. Observe the IP address displayed next to eth0, under “inet addr”. You can also see your IP address if you click the Network icon in the upper-right corner of your desktop, and then select “Connection Information”.

2. Install openssh-server by typing the following at the terminal:

   sudo apt-get install openssh-server
   

3. Just in case, restart the virtual machine.

Now you can connect from PuTTY using the IP address from step 1 above and port 22.

My resolution was similar to Roman T’s however I needed to add a few extra steps. In my case I had Ubuntu Server 14 VM running on a Windows 8 Desktop in Windows 2008 domain. If I tried NAT or Bridge I could access the Internet but couldn’t connect via SSH.

If I tried Host Only Adapter then that would allow me to SSH to machine but couldn’t access the Internet.

I tried Port forwarding as well and no joy. Opened up Wireshark and it just wasn’t finding VM.

So my solution was to add a second network adapter.

Method

With VM powered down

1. Click Settings > Network Click Adapter 1 and choose Bridged Adapter
2. Click Adapter 2 and choose Host Only Adapter
3. Click File > Preferences > Networks Under NAT Networks if you don’t see a NAT Network click on + icon to add NAT Network.
4. Click Host-Only Networks if you don’t see a host only network click + icon to add one

Start up VM

1. In order to see network adapter you need to type

   ifconfig -a
   

2. You may see the network adapter is added with a mac address but not an IP?

3. If so then you need to edit /etc/network/interfaces in order to configure DHCP. Example below using VI/VIM but you can use editor of your choice

   sudo vi /etc/network/interfaces
   

4. add the lines

   auto eth1
   iface eth1 inet dhcp
   

5. save and exit file.

6. Then try restarting network service using below command

   sudo service networking restart
   

7. Or if that fails then restart VM.

8. Once restarted type below to see if you eth1 has been allocated an IP address

   ifconfig -a
   

9. if so then see if you can SSH on to the VM

For Ubuntu 18.04 and VirtualBox 5.2:

1. Create a Host Network Interface

   i. On Virtualbox, click File/Host Network Manager.

   ii. If you don’t already have a Host Network adapter (default vboxnet0), click Create.

2. Enable Host-only Adapter settings for VM

   i. On Virtualbox, right click on your VM and select Settings.

   ii. Click Network and select Adapter 2.

   iii. Click Enable Network Adapter.

   iv. Under Attached to: select Host-only Adapter. The name of the adapter you created in step 1 should appear (default vboxnet0).

3. Configure network settings in VM

   i. Start your VM and check which interface was added: ip a. Look for the interface that doesn’t have an inet address. On mine, it was enp0s8.

   ii. Edit /etc/netplan/01-netcfg.yaml. e.g. sudo vi /etc/netplan/01-netcfg.yaml.

   iii. Under the settings for the original adapter, add configuration details:

   enp0s8:
       addresses: [192.168.56.2/24]
       gateway4: 192.168.56.1
       dhcp4: no
   

   This assigns a static ip address for your VM for SSH convenience. If you want dhcp to handle the addressing instead, leave out the address and gateway config and set dhcp4 to yes.

   iv. Reload the configuration file: sudo netplan apply.

4. SSH into your VM

   i. If you have not installed ssh in the VM: sudo apt install ssh.

   ii. From your host machine, SSH into the VM: ssh <username>@192.168.56.2.