computer science

Rensenware

Rensenware is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Rensenware rather than just read about it. In short: Rensenware (Korean: 련선웨어; Japanese: 蓮船ウェアー; stylized as rensenWare) is a ransomware that infects Windows computers. It was created as a joke by Kangjun Heo (허강준; alias "0x00000FF") and first appeared in 2017.

Key takeaways

Rensenware belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Rensenware to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Rensenware from memory before moving on to harder problems.

Reference excerpt

Rensenware (Korean: 련선웨어; Japanese: 蓮船ウェアー; stylized as rensenWare) is a ransomware that infects Windows computers. It was created as a joke by Kangjun Heo (허강준; alias "0x00000FF") and first appeared in 2017. Rensenware is unusual as an example of ransomware in that it does not request the user pay the creator of the virus to decrypt their files, instead requiring the user to achieve a required number of points in the shoot 'em up video game Undefined Fantastic Object before any decryption can take place. The main window displays Minamitsu Murasa, a character from the game. Heo released a patch that neutralizes Rensenware after the malware gained attention.

Description Rensenware was developed by Korean undergraduate student and programmer Kangjun Heo for Windows operating systems out of boredom as a joke within the Touhou Project fandom. When executed, the program scans and encrypts files on the computer ending in specific extensions using AES-256 and appends ".RENSENWARE" to the filename. The ransomware was first discovered by MalwareHunterTeam on April 6, 2017.

Payload Once the files have been encrypted, a warning window depicting the character Minamitsu Murasa from the Touhou Project is displayed, which cannot be closed. The program requires the user to play the bullet hell video game Touhou Seirensen ~ Undefined Fantastic Object, which is not included with the software meaning they must download it on their own, and score at least 200 million points in the "Lunatic" level of difficulty before any decryption may take place (the program automatically detects the game's process "th12" and its accumulated points). The payload window advises the user not to kill the Rensenware main program until their files have successfully been decrypted, otherwise they will lose them permanently as the decryption keys are not locally stored.

Neutralisation tool Heo later released a piece of software—setting the score in game's memory directly and satisfying the Rensenware requirements—onto GitHub with an apology. He also released a small part of the ransomware's source code without the payload.

Notes

References

External links rensenWare on GitHub

Worked examples

Example 1 — a first encounter with Rensenware

Start with the simplest possible case. Write down what Rensenware claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Rensenware before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Rensenware ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Rensenware

In research: Rensenware appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Rensenware in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Rensenware is common in secondary-school and first-year university syllabi. It links to neighbouring topics 2010s in hacking, 2017 in computing, Derivative works of Touhou Project, so understanding it makes those chapters shorter.
In everyday life: Look for Rensenware outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Rensenware in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Rensenware means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Rensenware out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Rensenware in simple terms?

Why does Rensenware matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Rensenware?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Rensenware.