<<< JPCERT/CC Alert 2017-06-28 >>>
Alert regarding PCs and servers that may be attacked via the Internet
Internet-reachable PCs and servers without adequate security measures
are under a risk of being exploited by an attacker which may result in
network intrusion or being used as a stepping-stone to further attack
JPCERT/CC has received multiple reports regarding mobile PCs (the connect
to a corporate network from a remote location) as well as servers and
PCs with a global IP address assigned for remote administration being
infected with malware or taken over by an attacker.
Over the past few months, JPCERT/CC has observed large scale damages
caused by the same cause. Therefore, this alert is issued together with
other security organizations in Japan to warn network administrators
Alert regarding ransomware "WannaCrypt" (last update: 2017-05-17)
Alert regarding vulnerability (CVE-2016-7836) in SKYSEA Client View (last update: 2017-03-08)
Network administrators and users should refer to the information in
"II. Solution" and "III. References" to check whether your PC or servers
are not accidentally exposed to the Internet and take proper security
[image 1: Security measures to protect PC from Internet-based attacks]
Check (1) and consider the countermeasures listed in (2) through to (5).
Applying multiple countermeasures reduces the risk against threats on
(1) Confirm whether the devices are not accessible from the Internet
Please confirm whether the device is not exposed to the Internet by
checking the IP address of the PC or server to make sure that no global
IP address is assigned to the device.
In particular, attention needs to be paid when using a data communication
card or a modem to connect to the Internet. If a global IP address is
unintentionally assigned to the device, as a result, the device will
be accessible from the Internet. Also, depending on the Internet service
provider, a private IP address may be assigned when connecting to the
Internet. In such cases, it is also necessary to beware of access
attempts from external sources.
[Reference: How to check IP address (example of Windows10)]
1. From "Network and Sharing Center", select "Change Adapter Settings"
to display all adapters
2. Right click the adapter currently used for the connection and
from the pull-down menu select "Status"
3. In the "Details" window (network connection details), the IP
address can be found
For more details, please refer the manual for the OS or PC.
The assignment of IP address differs in each Internet service provider.
JPCERT/CC Open DNS Resolver Check Site can be useful to check the
source IP address.
Open DNS Resolver Check Site (Japanese)
(2) Apply necessary firewall settings
In order to prevent intrusions via Internet-based attacks, please
properly configure firewalls implemented by the OS or anti-virus
software. Furthermore, please ensure that all PCs and servers are
protected by a firewall.
As for Windows, the Windows Firewall setting differs depending on the
network profile. When connecting to a network outside of your
organization, we recommend that you select an appropriate profile.
In addition, blocking specific ports can be selected from "Advanced
setting" of "Windows Firewall" function.
Please consider using Windows Firewall to block the port used by
SMB v1, with reference to the following information.
[Reference: How to block the port used by SMB v1 (example of Windows10)]
1. From "Network and Sharing Center", select "Windows Firewall"
and then open "Advanced Settings"
2. In "Windows Firewall with Advanced Security", right-click
"Inbound Rules" and then select "New Rule"
3. In the "New Inbound Rule Wizard", turn ON the checkbox for "Port"
and select "Next"
4. Select "TCP" and enter 139, 445. Then click "Next"
5. Check "Block the connection" and click "Next"
6. Select the profile to be enabled and click "Next"
7. For "Name" and "Description", enter appropriate text naming the
rule and click "Finish"
Furthermore, different applications and services use different ports.
For SKYSEA's communication method and ports, please refer to the
[Reference: List of ports used by SKYSEA]
SKYSEA use a different communication method for internal and external
hosts. Please apply appropriate configurations for each network profile.
SKYSEA Client View Ver.12 Communication Ports
For details about setting firewall function in an OS and anti-virus
software, please refer to the manual accordingly.
(3) Disable any unnecessary services
In order to prevent intrusions or unauthorized access through the
network, please check whether any unnecessary or unknown services are
available, and consider disabling them.
How to enable and disable SMBv1, SMBv2, and SMBv3 in Windows and Windows Server
(4) Update OS and Software
Please update the OS and software and use the version that addresses
vulnerabilities. Also, please consider using anti-virus software and
update the patch files regularly.
(5) Re-check default settings
In order to prevent Internet-based attacks, appropriately configure
services and login passwords, etc. In particular, if you are using
software that can remotely control your PC, a weak password may allow
an attacker intrusion.
Alert "Beware of settings for systems and devices connected to the network" (Japanese)
Japan Cybercrime Control Center (JC3)
Security countermeasures for PC's with global IP addresses directly assigned (Japanese)
Information-technology Promotion Agency (IPA)
Security environment that users should check - lessons learned from consultation on WannaCryptor (Japanese)
Internet Threat Monitoring Quarterly Report
National Police Agency
Access observations to 445/TCP from PCs that have been exploited by ransomware "WannaCry" (Japanese)
Security vulnerabilities in SKYSEA Client View (Japanese)
If you have any information regarding this alert, please contact
JPCERT Coordination Center (JPCERT/CC)
TEL: +81-3-3518-4600 FAX: +81-3-3518-4602