Archive for the ‘ Security ’ Category

如何解決 TLS/SSL 使用了不安全的加密演演算法: ARCFOUR、CBC、HMAC-MD5、HMAC-RIPEMD160

弱點掃瞄

弱點: TLS Service Supports Weak Cipher Suite

Transport Layer Security (TLS), the successor to Secure Socket Layer (SSL), is a network protocol that encrypt communications between TLS servers (e.g., websites) and TLS clients (e.g., web browsers). Every communication is secured by a cipher suite: a combination of several algorithms working in concert. Cryptographic algorithms do not have a defined lifetime, but academics, researchers, and nation states are constantly evaluating them for weaknesses. Consensus on which algorithms are untrustworthy evolves over time, and if a communication is protected with a weak cipher suite then that communication can be altered or decrypted.

  • Severity: Medium
  • Risk: A TLS service was observed supporting weak cipher suites.
  • Recommendation: Disable the cipher suites listed in the evidence column of the measurement.

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如何解決 SSH Server 使用了不安全的加密演演算法: ARCFOUR、CBC、HMAC-MD5、HMAC-RIPEMD160

弱點掃瞄

弱點 1: SSH Supports Weak Cipher

The SSH server is configured to support either Arcfour or Cipher Block Chaining (CBC) mode cipher algorithms. SSH can be configured to use Counter (CTR) mode encryption instead of CBC. The use of Arcfour algorithms should be disabled.

  • Severity: Medium
  • Risk: A weak cipher has been detected.
  • Recommendation: Configure the SSH server to disable Arcfour and CBC ciphers.

弱點 2: SSH Supports Weak MAC

The SSH server is configured to support MD5 algorithm. The cryptographic strength depends upon the size of the key and algorithm that is used. A Modern MAC algorithms such as SHA1 or SHA2 should be used instead.

  • Severity: Medium
  • Risk: A weak Message Authentication Code (MAC) algorithm has been detected.
  • Recommendation: Configure the SSH server to disable the use of MD5.

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如何解決 Web/Mail Server 使用了不安全的 SSL 通訊協定

弱點掃瞄

弱點: SSL/TLS Service Supports Weak Protocol

Transport Layer Security (TLS), the successor to Secure Socket Layer (SSL), is a network protocol that encrypt communications between TLS servers (e.g., websites) and TLS clients (e.g., web browsers). Every communication is secured by a cipher suite: a combination of several algorithms working in concert. Networking protocols do not have a defined lifetime, but academics, researchers, and nation states are constantly evaluating them for weaknesses. Consensus on which protocols are untrustworthy evolves over time, and if communications are sent with a weak protocol then that communication can be altered or decrypted.

  • Severity: High
  • Risk: A TLS service was observed supporting weak protocols.
  • Recommendation: Disable the protocols listed in the evidence column of the measurement.

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如何自動將網站的 http:// 網址轉址為 https://

弱點掃瞄

弱點: Site does not enforce HTTPS

The site responds to HTTP requests without ultimately redirecting the browser to a secure version of the page. Since the site allows plaintext traffic, a man-in-the-middle attacker is able to read and modify any information passed between the site and the user. There are a variety of situations in which an attacker can intercept plaintext traffic in a man-in-the-middle position, including but not limited to:

  1. Open Wi-Fi Hotspots
  2. WPA/WPA2 encrypted hot-spots where the attacker connected before the victim
  3. Malicious Wi-Fi access points
  4. Compromised switches and routers
  5. ARP poisoning on the same wired network

It's important to remember that in many of the above situations, an attacker can not only read traffic, but also actively modify the traffic. Even if a site that does not contain sensitive information, an attacker can still inject malicious content to a user』s browser.

  • Severity: High
  • Risk: Site does not enforce the use of HTTPS encryption, leaving the user vulnerable to man-in-the-middle attackers (who can falsify data and inject malicious code).
  • Recommendation: Any site served to a user (possibly at the end of a redirect chain) should be served over HTTPS.

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WannaCry 勒索病毒與 Windows 安全性更新檔下載網址

這兩天 WannaCry (WanaCrypt0r 2.0) 勒索病毒肆虐,台灣成為全球第二重災區!!

這個病毒是針對 Windows 的 SMB 漏洞進行攻擊,大部分其他病毒均是透過執行病毒所感染的檔案來傳播,與其他病毒不同的是,WannaCry 勒索病毒具有自行在「區域網路」擴散的能力

目前確定會遭受感染的作業系統為 Windows XP/Vista/7/8/8.1/10、Windows Server 2003/2008/2012,意思就是所有的 Windows 版本都會遭受感染

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解決 Chrome 遺失 chrome_elf.dll 的問題

最近我的 Google Chrome 瀏覽器常出問題,不知道從哪一版開始,當要從外部的程式開啟網頁時,就會出現遺失「chrome_elf.dll」的問題:

除了出現這個錯誤之外,經常還會有網頁打不開,或是網頁停止回應的狀況!!

一開始以為是裝了哪個擴充套件造成,但問題一直解決不了!!

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[JavaScript]如何防止自己的網站被別人以 iframe 蓋台嵌入 (與反制辦法)

「iframe (內置框架)」是用來在網頁中的特定位置嵌入另一個網頁。目前 Facebook、Google+、Twitter...等用來在網頁上顯示社群內容的社群元件,幾乎都是以 iframe 實作出來的。

原本框架是一種很好的應用,但如果是自己辛苦製作的網頁被別人的網站以 iframe 嵌入,因而出現在別人的網站裡,成為別人網站的一部份!!這種感覺就像是自己的心血被別人整碗捧走一樣!!

導回自已網站的方法

方法 1

於網頁的原始碼加入以下 Script:

<script type="text/javascript">
if( top.location != document.location ){
	top.location.href = document.location.href;
}
</script>

以上的 Script 會檢查瀏覽器最上層視窗的網址是否與目前網頁的網址一致,如果不一致,則把最上層視窗的網址改為目前網頁的網址,就醬。

方法 2 (反制辦法)

於網頁的原始碼加入以下 Script:

<script type="text/javascript">
if( top.location != document.location ){
	document.write("<h1 style='color:#FF0000'>未經授權嵌入別人的網頁是可恥的行為!!</h1>(<a href='"+document.location+"' target='_blank'>原站網址</a>)");
}
</script>

以上的 Script 會檢查瀏覽器最上層視窗的網址是否與目前網頁的網址一致,如果不一致,就顯示:

未經授權嵌入別人的網頁是可恥的行為!!
(原站網址)

我比較不喜歡與人家互嗆,所以我通常是用「方法 1」啦!

勒索病毒 (RansomWare) - 一種全新的商業模式

勒索病毒 (RansomWare)

近兩年來出現一種新型態的電腦病毒:「勒索病毒」。(關鍵字: RansomWare、Crypt0L0ocker、CryptoLocker、CryptWall)

這種病毒會將受害人電腦裡的文件類型的檔案加密 (包含連結到 NAS 的檔案),而受害人必須交付贖款才能取得解密程式。

由於病毒是使用很高階的加密技術,受害人即使能刪除病毒也救不回被加密的檔案。防毒軟體頂多能移除病毒,但仍無法解密檔案! 因此只能選擇交付贖款或放棄所有檔案。

而台灣的受害人甚至必須到「全家便利商店」購買 BitCoin 來付贖款,就算請店員打 165 也沒用!

唯有異地的檔案備份才能解除危機。

這種「勒索病毒」嚴然成為了一種新的「商業模式」,並且已經做出了口碑,未來只會衍生出更多的變種病毒。

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談電腦防毒、網路安全與帳戶安全

本文是綜合我的經驗,以及身為一個 MIS 的血淚所交織出來的資安重點,寫的不算專業,但還是希望對於看到的人能有一點幫助。

防毒觀念

  1. 病毒也是一種「軟體」,必須有人去執行。散播病毒的人會設法引誘你去執行它。
  2. 防毒軟體只能防「已知病毒」,新的病毒必需在有人中毒並且回報病毒樣本之後才能研發出病毒碼。直到防毒軟體能全面防止新病毒通常是病毒已經肆虐了好幾天之後的事情了。
  3. 寫病毒的人如果覺得有利可圖,病毒會更新的比防毒軟體還勤快!!
  4. 個人的安全意識比防毒軟體更為重要,人的因素,永遠是資安最大的漏洞。

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Linux 電子郵件防毒: ClamAV + Sendmail

本文要介紹的 Linux 的 E-Mail 防毒主要由兩個套件組成: clamav 與 clamav-milter。

其中「clamav」是防毒軟體、「clamav-milter」是 clamav 用來與 sendmail 整合的掃毒程式。

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