Подозрительное списание может быть мошеннической операцией: получатель неизвестен.

In this sentence, списание is a banking/financial word. It means something like:

• debit
• charge
• withdrawal
• write-off from an account

So подозрительное списание is not about copying homework. It means a suspicious amount of money being taken from an account or charged to a card.

This is very common in bank notifications and fraud warnings.

Because списание is a neuter noun.

So the adjective has to agree with it:

• masculine: подозрительный
• feminine: подозрительная
• neuter: подозрительное

Here:

• списание = neuter singular
• therefore подозрительное = neuter singular nominative

Может быть here means may be / could be.

It is made of:

• может = can / may
• быть = to be

So literally: A suspicious charge may be a fraudulent transaction.

You need быть because может is the modal verb, and быть is the infinitive that goes with it.

Compare:

• Это может быть ошибкой. = This may be a mistake.
• Он может прийти. = He may come.

In the present tense, Russian often omits is/are, but after a modal like может, you still use the infinitive быть if you mean may be.

Because after быть, Russian often uses the instrumental case for the noun that describes what something is.

So:

• операция = nominative
• операцией = instrumental

And the adjective must match:

• мошенническая операция = a fraudulent transaction
• мошеннической операцией = as a fraudulent transaction / be a fraudulent transaction

So:

• может быть мошеннической операцией = may be a fraudulent transaction

This instrumental predicate is very common, especially after forms like:

• быть
• стать
• являться
• оказаться

It agrees with операцией.

The noun операция is:

• feminine
• singular
• instrumental

So the adjective must also be:

• feminine
• singular
• instrumental

That gives:

• мошеннической операцией

Base form:

• мошенническая операция

After быть in this structure:

• мошеннической операцией

It is omitted.

In the present tense, Russian normally does not use a word for is/am/are.

So:

• получатель неизвестен literally looks like recipient unknown
• but it means the recipient is unknown

This is completely normal Russian.

Compare:

• Он дома. = He is at home.
• Она занята. = She is busy.
• Получатель неизвестен. = The recipient is unknown.

Неизвестен is the short-form adjective, and here it is used as the predicate: is unknown.

Russian often uses:

• long form adjectives for describing a noun directly
• short form adjectives for saying what something is like in the sentence

So:

• неизвестный получатель = an unknown recipient
  
  • this is a noun phrase
• получатель неизвестен = the recipient is unknown
  
  • this is a full statement

In formal written Russian, especially in notices and alerts, short forms like неизвестен are very common.

Because получатель is masculine singular.

The short-form adjective must agree with it:

• masculine: неизвестен
• feminine: неизвестна
• neuter: неизвестно
• plural: неизвестны

So:

• получатель неизвестен = the recipient is unknown
• получательница неизвестна = the female recipient is unknown
• имя неизвестно = the name is unknown

The colon introduces an explanation or reason.

So the structure is:

• Подозрительное списание может быть мошеннической операцией:
  explanation follows
• получатель неизвестен.

In natural English, the second part gives the reason why the charge is suspicious:

• it may be fraudulent: the recipient is unknown

Russian often uses a colon this way in warnings, notices, and formal messages.

The current word order is the most neutral and natural for a formal alert:

• Подозрительное списание может быть мошеннической операцией: получатель неизвестен.

Some parts could be rearranged, but the tone or emphasis would change. For example:

• Получатель неизвестен. = neutral statement
• Неизвестен получатель. = more marked, more emphasis on unknown

In bank or app notifications, Russian usually prefers the straightforward, neutral order used here.