Ransomware is a category of malicious software designed to deny an organization or individual access to systems or data, most commonly by encrypting files and demanding payment for their recovery. Modern ransomware operations can be considerably more sophisticated than a single malicious program running on one computer.

In a business environment, attackers may first obtain access through phishing, stolen credentials, vulnerable internet-facing services, compromised remote-access systems, or another malware infection. They may then spend time discovering servers, user accounts, backups, network shares, security tools, and other valuable resources before deploying ransomware.

This distinction is important because the ransomware encryption event may be the final stage of a much larger intrusion rather than the beginning of the attack.

A ransomware incident can potentially affect:

• Local hard drives and SSDs
• USB and other removable storage
• Mapped network drives
• Windows shared folders
• File servers
• NAS devices
• Accessible backup repositories
• Virtualization infrastructure
• Cloud-synchronized folders
• Files synchronized through services such as OneDrive, SharePoint, Google Drive, and Dropbox
• Other computers reachable with compromised credentials or exploitable vulnerabilities

The exact impact depends on the ransomware family, the attacker's access, network architecture, account permissions, security controls, and backup design.

1. How Does Ransomware Get Into a Computer or Business Network?

There is no single ransomware infection method. Attackers use several initial-access techniques.

1. Phishing Emails

Phishing remains an important method for delivering malware or stealing credentials.

An attacker may send an email pretending to be:

• A bank
• Customer
• Vendor
• Courier company
• Government department
• Tax authority
• Microsoft 365 administrator
• Google account notification
• HR department
• Senior executive

The email may contain a malicious attachment or direct the victim to a malicious website.

Common suspicious attachments include:

• ZIP archives
• Executable files
• Script files
• Disk images
• Shortcut files
• Documents designed to persuade the user to perform unsafe actions

Modern Office security features have made some older macro-based techniques less convenient for attackers, but social engineering continues to evolve.

Typical attack sequence

Phishing email → User interaction → Credential theft or malware execution → Attacker establishes access → Privilege escalation/lateral movement → Ransomware deployment

The ransomware itself does not necessarily arrive directly in the original email. The initial payload can be a downloader, information stealer, remote-access malware, or another tool that provides attackers with access.

2. Malicious Links and Fake Websites

Instead of attaching malware, attackers can persuade users to visit malicious websites.

Examples include fake:

• Microsoft 365 login pages
• Google login pages
• Cloud document-sharing pages
• Invoice portals
• Courier tracking websites
• Software download pages
• CAPTCHA/security verification pages
• Browser update pages

A particularly dangerous outcome is credential theft.

For example:

User opens fake Microsoft 365 page → Enters username/password → Credentials reach attacker → Attacker attempts account or remote-service access

Multi-factor authentication significantly improves protection, although organizations should still use phishing-resistant authentication where appropriate and monitor suspicious sign-ins.

3. Remote Desktop Protocol (RDP) and Other Remote-Access Services

Poorly secured remote access can create a serious ransomware risk.

Attackers may attempt to gain access using:

• Stolen RDP credentials
• Password spraying
• Credential stuffing
• Weak passwords
• Previously compromised administrator credentials
• Exposed remote-management services
• Vulnerabilities in remote-access software

Once attackers obtain interactive access to a server or workstation, they may behave similarly to legitimate administrators.

They can potentially investigate the network, locate data, disable protections, access backups, and distribute ransomware.

Important RDP security practices

Avoid exposing RDP directly to the public Internet whenever possible.

Organizations should consider:

• VPN or secure remote-access gateways
• Multi-factor authentication
• Network Level Authentication
• Strong unique passwords
• Account lockout/rate-limiting policies
• Restricted administrative access
• Firewall allow-listing where practical
• Continuous monitoring of remote logins
• Timely Windows security updates

4. Exploiting Unpatched Software Vulnerabilities

Ransomware operators and their affiliates may exploit vulnerabilities in internet-facing systems.

Possible targets include:

• VPN appliances
• Firewalls
• Web servers
• File-transfer software
• Remote-management products
• Windows servers
• Virtualization platforms
• Business applications

An organization can therefore be compromised even without an employee opening a malicious email.

This makes vulnerability and patch management a fundamental part of ransomware prevention.

5. Compromised Credentials

Credentials are extremely valuable during ransomware attacks.

Attackers may obtain passwords through:

• Phishing
• Information-stealing malware
• Password reuse
• Credential stuffing
• Data breaches
• Weak passwords
• Compromised endpoints
• Malicious browser extensions
• Credential dumping after gaining system access

The consequences become much more serious when the compromised account has:

• Local administrator rights
• Domain administrator rights
• Backup administrator privileges
• Server access
• VPN access
• Remote Desktop access
• Cloud administrator privileges

Organizations should therefore apply the principle of least privilege.

A normal employee should not routinely operate with domain-wide administrative privileges.

6. Malware Loaders and Existing Infections

Sometimes ransomware is not the first malware installed.

An initial malware infection may establish access to the system. Attackers can subsequently use that access to deploy additional payloads.

A simplified chain could look like:

Malicious email → Initial malware → Command-and-control access → Credential theft → Network discovery → Ransomware deployment

Therefore, detecting an apparently unrelated malware infection should be treated seriously.

7. Compromised Software and Supply-Chain Attacks

Attackers can sometimes compromise:

• Software vendors
• Managed service providers
• Software update mechanisms
• Remote-management platforms
• Third-party service providers

If trusted software or management infrastructure is compromised, attackers may potentially reach multiple customer environments.

These attacks demonstrate why organizations must evaluate not only their own security but also third-party access.

8. What Happens When a Computer Is Infected With Ransomware?

The exact sequence varies substantially between ransomware families.

A simplified technical ransomware lifecycle may include the following stages.

Stage 1: Initial Execution

A malicious payload executes on the endpoint.

It may be launched through:

• An executable
• Script
• Malicious document chain
• Software exploit
• Remote administration session
• Malware loader
• Scheduled task
• PowerShell or another legitimate administrative mechanism abused by attackers

Stage 2: Environment Discovery

Attackers or malware may identify the surrounding environment.

Information of interest can include:

• Computer name
• Windows version
• Logged-in user
• Domain membership
• IP addresses
• Network configuration
• Connected drives
• Mapped drives
• Shared folders
• Running processes
• Security products
• Backup software
• Domain controllers
• File servers

Human-operated ransomware intrusions may involve extensive discovery before encryption begins.

Stage 3: Privilege Escalation

Attackers frequently attempt to obtain higher privileges.

The objective may be to gain:

• Local administrator access
• SYSTEM privileges
• Domain administrator credentials
• Backup administrator access
• Virtualization administration privileges

Higher privileges can significantly increase the potential impact of an attack.

Stage 4: Security Defense Evasion

Attackers may attempt to interfere with security controls.

Possible targets include:

• Endpoint security
• EDR agents
• Logging
• Backup services
• Windows services
• Recovery mechanisms

Modern security platforms often include tamper-protection features specifically to make unauthorized modification more difficult.

Stage 5: Backup and Recovery Targeting

Sophisticated attackers understand that reliable backups reduce the victim's incentive to pay.

Consequently, attackers may attempt to identify and damage accessible backup systems before encrypting production data.

Potential targets include:

• Online backup repositories
• Network backup shares
• NAS devices
• Backup servers
• Hypervisor snapshots
• Windows shadow copies
• Recovery partitions
• Backup administrator accounts

This is why simply having "a backup" is not sufficient.

Organizations need a backup architecture that includes isolation and recovery testing.

9. Data Exfiltration Before Encryption

Many modern ransomware operations use a double-extortion strategy.

Attackers may steal information before encrypting it.

Potentially valuable data includes:

• Financial records
• Customer information
• Employee information
• Contracts
• Databases
• Internal documents
• Intellectual property
• Emails
• Authentication information

The attacker can then threaten to publish stolen data even if the victim can restore encrypted systems from backups.

Therefore:

Successful restoration from backup does not automatically eliminate the security incident.

Organizations must also investigate whether sensitive information was accessed or exfiltrated.

10. File Encryption

The ransomware may enumerate accessible files and encrypt selected file types.

Common targets can include:

• Documents
• Spreadsheets
• PDFs
• Images
• Databases
• Accounting files
• Project files
• Archives
• Business application data

Ransomware commonly uses efficient cryptographic designs involving symmetric encryption for data and asymmetric cryptography for protecting encryption keys, although implementation varies between ransomware families.

After encryption, filenames or extensions may also be changed.

For example:

Accounts.xlsx

could become something resembling:

Accounts.xlsx.<ransomware-extension>

The exact naming convention depends on the ransomware.

11. Ransom Note Creation

After encryption, ransomware commonly creates a ransom note.

It may appear as:

• TXT file
• HTML file
• Desktop wallpaper
• Popup window

The note may claim that files have been encrypted and provide payment or communication instructions.

Organizations should avoid immediately paying or contacting attackers without involving qualified incident-response, legal, management, insurance, and relevant law-enforcement resources as appropriate.

12. What Are the Most Common Ways Ransomware Spreads?

It is useful to distinguish initial access from lateral movement.

Initial access gets the attacker into the organization.

Lateral movement allows the attacker to move from the originally compromised system to additional systems.

Common mechanisms include:

1. Phishing and malicious email
2. Credential theft
3. Compromised remote access
4. Exploitation of vulnerabilities
5. Malware loaders
6. Weak or reused passwords
7. Compromised administrator accounts
8. Windows administrative services
9. Shared network resources
10. Remote-management software
11. Poorly segmented networks
12. Compromised third-party access

Not every ransomware variant automatically propagates like a computer worm. In many major incidents, human attackers deliberately move through the network before deploying ransomware centrally.

13. Can Ransomware Spread Across a Local Network?

Yes.

A ransomware incident can potentially spread or be deployed across a LAN, especially when the attacker obtains privileged credentials.

Imagine an office with:

PC-01 → PC-02 → File Server → Accounting Server → Backup Server → NAS

If PC-01 is compromised, the attacker may attempt to discover and reach the other systems.

Network discovery can reveal:

• Other Windows computers
• Servers
• File shares
• Domain controllers
• NAS systems
• Backup infrastructure
• Remote-management systems

Weak segmentation can make lateral movement easier.

14. Why Active Directory Can Increase the Impact

Active Directory itself is not the cause of ransomware, but compromised privileged domain credentials can give attackers extensive control over a Windows environment.

If an attacker gains sufficient privileges, they may potentially deploy ransomware to many computers using legitimate administrative capabilities.

That is why privileged accounts should be strongly protected.

Recommended practices include:

• Separate administrator accounts
• No routine web browsing from privileged accounts
• MFA where supported
• Privileged access workstations where appropriate
• Restricted RDP access
• Strong password policies
• Least privilege
• Monitoring of privileged logins
• Protection of domain controllers
• Network segmentation

15. Can Ransomware Encrypt Network Drives and Shared Folders?

Yes. This is one of the most important ransomware risks for businesses.

Suppose an employee has these mapped drives:

C: Local computer
D: Local data
F: Finance server
S: Shared company files
Z: NAS storage

If the compromised account has write access to F:, S:, and Z:, ransomware running under that user's context may be able to modify or encrypt files accessible through those locations.

The fundamental principle is:

Ransomware can potentially damage data that the compromised process or account has permission to modify.

Therefore, excessive user permissions increase ransomware exposure.

16. UNC Network Shares Can Also Be at Risk

A drive does not necessarily need to be mapped with a drive letter.

Files accessed through UNC paths may also be exposed.

For example:

\\FILESERVER\Accounts

\\SERVER01\CompanyData

\\NAS01\Backup

If the infected account can write to the location, ransomware may potentially encrypt or otherwise damage those files.

17. Can Ransomware Encrypt NAS Devices?

Potentially, yes.

A NAS may be affected if ransomware can access its shares using credentials available to the compromised computer or attacker.

The risk is especially serious when:

• Every user has write access
• Backup shares remain permanently mounted
• NAS administrative passwords are weak
• NAS management interfaces are exposed to the Internet
• Snapshots are unavailable
• Backup and production credentials are identical

NAS snapshots and protected versions can be extremely valuable, but they should be configured so an ordinary compromised workstation cannot simply delete them.

18. Can Ransomware Encrypt Cloud-Synced Files?

Yes.

This is commonly misunderstood.

Consider a Windows PC synchronized with:

C:\Users\User\OneDrive\Company

If ransomware encrypts files inside that local synchronized directory, the synchronization client may interpret those encrypted files as legitimate modifications.

The synchronization process can then upload the changed files to the cloud.

Conceptually:

Original cloud file → Local synchronized copy → Ransomware encrypts local copy → Sync client detects modification → Encrypted version synchronizes

This does not necessarily mean that ransomware directly compromised the cloud provider.

Instead, the legitimate synchronization software may synchronize the ransomware-induced changes.

19. OneDrive and SharePoint

Files synchronized locally through Microsoft OneDrive or SharePoint libraries may therefore be affected by ransomware activity on an endpoint.

Microsoft cloud services provide recovery and versioning capabilities that may help recover previous versions, depending on configuration, retention, attack circumstances, and administrative actions.

Organizations should not treat synchronization alone as backup.

Synchronization and backup serve different purposes.

20. Google Drive and Dropbox

A similar principle can apply to other synchronization platforms.

If a locally synchronized file is encrypted and the synchronization client uploads that modification, cloud copies may be affected.

Recovery may be possible using:

• File version history
• Deleted-file retention
• Administrative recovery
• Cloud backup
• Provider-specific recovery features

Capabilities and retention periods vary, so administrators should verify current settings before an incident occurs.

21. Cloud Sync Is Not the Same as Cloud Backup

This distinction is critical.

Synchronization

Designed primarily to keep files consistent across devices.

If:

File A → File A.encrypted

the modification may synchronize.

Backup

Designed to preserve recoverable historical copies.

A strong backup platform should allow administrators to restore data to a point before the ransomware attack.

Businesses using Microsoft 365, Google Workspace, or other SaaS platforms should evaluate whether their recovery requirements justify a separate backup service in addition to built-in retention and versioning.

22. Can Ransomware Encrypt Backup Files?

Yes, if the backup repository is accessible to the compromised system or credentials.

For example, a permanently mapped backup location such as:

X:\Backup

can create unnecessary exposure if normal users or compromised administrators can modify its contents.

Attackers may attempt to encrypt or delete:

• Backup archives
• System images
• Database backups
• Virtual machine backups
• NAS backups
• Shadow copies
• Online backup repositories

A backup that attackers can destroy is not sufficient protection against a sophisticated ransomware incident.

23. The 3-2-1 Backup Principle

A commonly recommended starting point is the 3-2-1 backup strategy:

• Maintain at least 3 copies of important data
• Store them on at least 2 different types of storage or systems
• Keep at least 1 copy off-site or otherwise isolated

Modern ransomware planning should go further by considering:

• Immutable backups
• Offline backups
• Separate backup credentials
• MFA for backup administration
• Protected retention
• Recovery testing
• Backup monitoring

An organization should know not only whether backups exist, but also whether they can actually restore the business within an acceptable time.

24. Network Segmentation Can Limit Ransomware Impact

A flat network allows many systems to communicate freely.

For example:

User PCs ↔ Servers ↔ NAS ↔ Backup Infrastructure

This can increase the potential blast radius.

A segmented environment separates systems according to their purpose and security requirements.

For example:

User VLAN → Application Servers

Server VLAN → Restricted Management Network

Backup Network → Highly Restricted Access

Guest Wi-Fi → Internet Only

Segmentation does not guarantee protection, but it can make lateral movement more difficult and provide defenders with additional control points.

25. How Businesses Can Reduce Ransomware Risk

An effective ransomware defense requires multiple layers.

Endpoint Protection

Use centrally managed endpoint protection or EDR where appropriate.

Keep tamper protection enabled whenever supported.

Patch Management

Regularly update:

• Windows
• Browsers
• Office
• VPN software
• Firewalls
• Server applications
• Remote-management software
• NAS firmware
• Hypervisors
• Business applications

Email Security

Use:

• Anti-phishing controls
• Attachment scanning
• URL filtering
• Domain authentication technologies such as SPF, DKIM, and DMARC
• User awareness training

Identity Security

Implement:

• MFA
• Strong unique passwords
• Least privilege
• Separate administrative accounts
• Restricted service accounts
• Conditional access where appropriate

Remote Access Security

Do not unnecessarily expose administrative services directly to the Internet.

Prefer controlled remote access through technologies such as:

• VPN
• Remote Desktop Gateway
• Zero-trust access solutions
• MFA-protected remote-management platforms

Network Security

Implement:

• Network segmentation
• Firewall rules between security zones
• Restricted SMB access
• Controlled administrative access
• Logging and monitoring

Backup Security

Maintain:

• Multiple backup copies
• Off-site copies
• Immutable or offline copies
• Separate backup credentials
• MFA
• Regular restore testing

26. What Should You Do If Ransomware Is Detected?

The first priority is usually containment.

Depending on the environment and incident-response plan, actions may include:

1. Isolate affected computers from the network.
2. Disconnect affected systems from Wi-Fi and Ethernet where necessary.
3. Prevent access to critical shares if active encryption is occurring.
4. Preserve evidence rather than immediately formatting every system.
5. Identify affected accounts and systems.
6. Reset compromised credentials from trusted systems when appropriate.
7. Investigate lateral movement.
8. Determine whether information was exfiltrated.
9. Protect unaffected backups.
10. Engage qualified incident-response professionals.
11. Follow applicable legal, regulatory, insurance, and reporting requirements.
12. Restore systems only after understanding and containing the intrusion.

Avoid reconnecting restored computers to a compromised environment before the original attack path has been addressed.

Otherwise, systems may be compromised again.

27. Example Business Ransomware Scenario

Consider a company with 30 Windows computers, one Active Directory server, one accounting server, a file server, NAS storage, Microsoft 365, and cloud-synchronized documents.

An attacker steals a user's remote-access credentials.

The attacker enters the network and eventually obtains administrative privileges.

They discover:

SERVER-DC

SERVER-FILE

SERVER-ACCOUNTING

NAS-BACKUP

The attacker then attempts to access additional credentials, identify backup systems, and distribute ransomware.

The file server is encrypted.

Employee PCs are encrypted.

Files in synchronized OneDrive directories are modified, and some encrypted modifications synchronize.

The NAS backup is also damaged because the compromised administrative account had excessive access.

This turns what began as one credential compromise into a business-wide incident.

A properly segmented network with MFA, restricted administrative accounts, EDR, protected backup credentials, and immutable backups could substantially reduce the potential impact.

Frequently Asked Questions (FAQ)

1. Can ransomware spread from one computer to another?

Yes. Some ransomware or associated malware can propagate automatically, while human attackers can also deliberately move laterally between computers using compromised credentials, vulnerabilities, administrative tools, or remote services.

2. Can ransomware spread through Wi-Fi?

Being connected to the same Wi-Fi network does not automatically mean ransomware will infect every device. However, if devices can communicate with one another and exploitable services or compromised credentials are available, the network may provide a path for lateral movement.

3. Can ransomware encrypt mapped drives?

Yes. If the ransomware process has write access to a mapped network drive, files on that drive may potentially be encrypted.

4. Can ransomware encrypt a server?

Yes. Windows servers, file servers, application servers, virtualization infrastructure, and other servers can be ransomware targets.

5. Can ransomware encrypt NAS storage?

Yes, particularly when NAS shares or administrative interfaces are accessible using compromised credentials.

6. Can ransomware encrypt OneDrive files?

Locally synchronized OneDrive files can be encrypted. The modified files may then synchronize to the cloud. Versioning and recovery features may help depending on the environment and retention configuration.

7. Can ransomware affect SharePoint?

Files synchronized from SharePoint to compromised endpoints may be modified and synchronized back. Attackers who compromise cloud identities may also attempt other destructive actions depending on their permissions.

8. Can ransomware encrypt Google Drive files?

Locally synchronized Google Drive files can potentially be encrypted, with those modifications subsequently synchronized. Recovery depends on available versions, retention, administrative controls, and backups.

9. Can ransomware affect Dropbox?

Yes. Locally synchronized Dropbox files can potentially be encrypted and synchronized. Version history or recovery functionality may help restore earlier versions depending on the account and applicable retention.

10. Does cloud storage completely protect against ransomware?

No. Cloud storage can provide valuable recovery features, but synchronization is not equivalent to an independent ransomware-resistant backup.

11. Can ransomware destroy backups?

Attackers may attempt to encrypt, delete, or otherwise disable accessible backups. Offline, isolated, or immutable backups provide stronger protection.

12. Will antivirus always stop ransomware?

No security product can guarantee detection of every attack. Endpoint security should be combined with patching, MFA, least privilege, segmentation, monitoring, secure backups, and user awareness.

13. Can ransomware attack a computer without administrator rights?

Yes. Malware running as a standard user may still encrypt files that user has permission to modify. Administrative privileges generally allow an attacker to cause much greater damage.

14. Does disconnecting the Internet stop ransomware?

Not necessarily. Ransomware already executing locally may continue encrypting accessible files even without Internet connectivity. Network isolation can nevertheless be crucial for containment.

15. Should I disconnect an infected computer from the network?

If active ransomware is suspected, isolating the affected endpoint from network connectivity is generally an important containment measure. In a business environment, follow the organization's incident-response procedure and involve security professionals.

16. Can ransomware spread through USB drives?

Some malware can infect or use removable media, although behavior depends on the malware family. Unknown USB devices should never be trusted automatically.

17. Does formatting an infected computer solve everything?

Formatting can remove malware from that particular endpoint, but it does not establish how attackers entered the environment, whether other computers remain compromised, whether credentials were stolen, or whether data was exfiltrated.

18. Can ransomware come back after restoring a backup?

Yes. If the original entry point, compromised credentials, persistence mechanisms, or other infected systems remain unresolved, restored systems can potentially be attacked again.

19. What is double-extortion ransomware?

Double extortion refers to attacks where criminals steal information in addition to encrypting systems and threaten to publish or misuse the stolen information if payment is not made.

20. What is the best protection against ransomware?

There is no single solution. Strong protection combines endpoint security, MFA, patch management, least privilege, network segmentation, secure remote access, monitoring, user education, and tested offline or immutable backups.

Conclusion

Ransomware should not be viewed simply as a virus that encrypts one computer.

Modern ransomware incidents can involve an entire attack chain:

Initial access → Credential compromise → Privilege escalation → Network discovery → Lateral movement → Backup targeting → Data theft → Ransomware deployment → Encryption → Extortion

A compromised workstation can become a gateway to file servers, mapped drives, NAS devices, business applications, backups, and cloud-synchronized information when network permissions and security controls allow it.

The most effective defense is therefore defense in depth.

Organizations should assume that individual security controls can eventually fail and design the environment so that one compromised user, workstation, or password cannot automatically compromise the entire business.

Strong identity protection, restricted privileges, segmentation, endpoint monitoring, patch management, secure remote access, and independently protected backups can dramatically reduce both the probability and business impact of a ransomware incident.

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