March 2, 2021

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They Come in the Night: Ransomware Deployment Trends

6 min read

Original Post from FireEye
Author: Kelli Vanderlee

Ransomware is a remote, digital shakedown. It is disruptive and
expensive, and it affects all kinds of organizations, from cutting
edge space
technology
firms, to the wool
industry
, to industrial
environments
. Infections have forced hospitals to turn
away patients
and law enforcement to drop
cases
against drug dealers. Ransomware operators have recently
begun combining encryption with the threat of data
leak and exposure
in order to increase leverage against victims.
There may be a silver lining, however; Mandiant Intelligence research
suggests that focusing defensive efforts in key areas and acting
quickly may allow organizations to stop ransomware before it is deployed.

Mandiant Intelligence examined dozens of ransomware incident
response investigations from 2017 to 2019. Through this research, we
identified a number of common characteristics in initial intrusion
vectors, dwell time, and time of day of ransomware deployment. We also
noted threat actor innovations in tactics to maximize profits (Figure
1). Incidents affected organizations across North America, Europe,
Asia Pacific, and the Middle East in nearly every sector category,
including financial services, chemicals and materials, legal and
professional services, local government, and healthcare. We observed
intrusions attributed to financially motivated groups such as FIN6,
TEMP.MixMaster, and dozens of additional activity sets.


Figure 1: Themes Observed in Ransomware Incidents

These incidents provide us with enhanced insight into ransomware
trends that can be useful for network defenders, but it is worth
bearing in mind that this data represents only a sample of all
activity. For example, Mandiant ransomware investigations increased
860% from 2017 to 2019. The majority of these incidents appeared to be
post-compromise infections, and we believe that threat actors are
accelerating use of tactics including post compromise deployment to
increase the likelihood of ransom payment. We also observed incidents
in which ransomware was executed immediately, for example GANDCRAB and
GLOBEIMPOSTER incidents, but most of the intrusions examined were
longer duration and more complex post-compromise deployments.

Common Initial Infection Vectors

We noted several initial infection vectors across multiple
ransomware incidents, including RDP, phishing with a malicious link or
attachment, and drive by download of malware facilitating follow-on
activity. RDP was more frequently observed in 2017 and declined in
2018 and 2019. These vectors demonstrate that ransomware can enter
victim environments by a variety of means, not all of which require
user interaction.

RDP or other remote access One of the most frequently observed vectors
was an attacker logging on to a system in a victim environment
via Remote Desktop Protocol (RDP). In some cases, the attacker
brute forced the credentials (many failed authentication
attempts followed by a successful one). In other cases, a
successful RDP log on was the first evidence of malicious
activity prior to a ransomware infection. It is possible that
the targeted system used default or weak credentials, the
attackers acquired valid credentials via other unobserved
malicious activity, or the attackers purchased RDP access
established by another threat actor. In April
2019
, we noted that FIN6 used stolen credentials and RDP
to move laterally in cases resulting in ransomware
deployment.
Phishing with link or attachment A significant number of ransomware
cases were linked to phishing campaigns delivering some of the
most prolific malware families in financially motivated
operations: TRICKBOT, EMOTET, and FLAWEDAMMYY. In January
2019
, we described TEMP.MixMaster TrickBot infections that
resulted in interactive deployment of Ryuk.
Drive-by-download Several ransomware infections were traced back
to a user in the victim environment navigating to a
compromised website that resulted in a DRIDEX infection. In October
2019
, we documented compromised web infrastructure
delivering FAKEUPDATES, then DRIDEX, and ultimately BITPAYMER
or DOPPELPAYMER infections.

Most Ransomware Deployments Take Place Three or More Days After
Initial Infection

The number of days elapsed between the first evidence of malicious
activity and the deployment of ransomware ranged from zero to 299 days
(Figure 2). That is, dwell times range quite widely, and in most
cases, there was a time gap between first access and ransomware
deployment. For 75 percent of incidents, at least three days passed
between the first evidence of malicious activity and ransomware deployment.

This pattern suggests that for many organizations, if initial
infections are detected, contained, and remediated quickly, the
significant damage and cost associated with a ransomware infection
could be avoided.
In fact, in a handful of cases, Mandiant
incident responders and FireEye Managed Defense contained and
remediated malicious activity, likely preventing ransomware
deployment. Several investigations discovered evidence of ransomware
installed into victim environments but not yet successfully executed.


Figure 2: Days elapsed between initial
access and ransomware deployment

Ransomware Deployed Most Often After Hours

In 76% of incidents we reviewed, ransomware was executed in victim
environments after hours, that is, on a weekend or before 8:00 a.m. or
after 6:00 p.m. on a weekday, using the time zone and customary work
week of the victim organization (Figure 3 and Figure 4). This
observation underscores that threat actors continue working even when
most employees may not be.

Some attackers possibly intentionally deploy ransomware after hours,
on weekends, or during holidays, to maximize the potential
effectiveness of the operation on the assumption that any remediation
efforts will be implemented more slowly than they would be during
normal work hours. In other cases, attackers linked ransomware
deployment to user actions. For example, in 2019 incidents at retail
and professional services firms, attackers created an Active Directory
Group Policy Object to trigger ransomware execution based on user log
on and log off.


Figure 3: Ransomware execution frequently
takes place after hours


Figure 4: Ransomware execution by hour of
the day

Mitigation Recommendations

Organizations seeking to prevent or mitigate the effects of
ransomware infections could consider the following steps. For more
comprehensive recommendations for addressing ransomware, please refer
to our blog post: Ransomware
Protection and Containment Strategies: Practical Guidance for
Endpoint Protection, Hardening, and Containment
and the
linked white paper.

Address Infection Vectors
  • Use enterprise network, email, and
    host-based security products with up-to-date detections to
    prevent and detect many common malware strains such as
    TRICKBOT, DRIDEX, and EMOTET.
  • Contain and remediate
    infections quickly to prevent attackers from conducting
    follow-on activity or selling access to other threat actors
    for further exploitation.
  • Perform regular network
    perimeter and firewall rule audits to identify any systems
    that have inadvertently been left accessible to the
    internet. Disable RDP and other protocols to systems where
    this access is not expressly required. Enable multi-factor
    authentication where possible, particularly to
    internet-accessible connections, see pages 4-15 of the white
    paper for more details.
  • Enforce multi-factor
    authentication, that is, where enabled, do not allow single
    factor authentication for users who have not set up the
    multi-factor mechanism.
Implement Best Practices
  • For example, carry out regular
    anti-phishing training for all employees that operate a
    device on the company network. Ensure employees are aware of
    threat, their role in preventing it, and the potential cost
    of a successful infection.
  • Implement network
    segmentation when possible to prevent a potential infection
    from spreading.
  • Create regular backups of critical
    data necessary to ensure business continuity and, if
    possible, store them offsite, as attackers often target
    backups.
  • Restrict Local Administrator accounts from
    specific log on types, see page 18 of the white paper for
    more details.
  • Use a solution such as LAPS to
    generate a unique Local Administrator password for each
    system.
  • Disallow cleartext passwords to be stored in
    memory in order to prevent Mimikatz credential harvesting,
    see p. 20 of the white paper for more details.
  • Consider cyber insurance that covers ransomware
    infection.
Establish Emergency Plans
  • Ensure that after-hours coverage is
    available to respond within a set time period in the case of
    an emergency.
  • Institute after-hours emergency
    escalation plans that include redundant means to contact
    multiple stakeholders within the organization and 24-hour
    emergency contact information for any relevant third-party
    vendors.

Outlook

Ransomware is disruptive and costly. Threat actor innovations have
only increased the potential damage of ransomware infections in recent
years, and this trend shows no sign of slowing down. We expect that
financially motivated actors will continue to evolve their tactics to
maximize profit generated from ransomware infections. We anticipate
that post-compromise ransomware infections will continue to rise and
that attackers will increasingly couple ransomware deployment with
other tactics, such as data theft and extortion, increasing ransom
demands, and targeting critical systems.

The good news is that particularly with post-compromise infections,
there is often a window of time between the first malicious action and
ransomware deployment. If network defenders can detect and remediate
the initial compromise quickly, it is possible to avoid the
significant damage and cost of a ransomware infection.

Register for our upcoming ransomware
webinar
to learn more.


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Author: Kelli Vanderlee

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